Field-effect transistor having amorphous composite metal oxide insulation film, semiconductor memory, display element, image display device, and system

ABSTRACT

A field-effect transistor includes a substrate; a source electrode, a drain electrode, and a gate electrode that are formed on the substrate; a semiconductor layer by which a channel is formed between the source electrode and the drain electrode when a predetermined voltage is applied to the gate electrode; and a gate insulating layer provided between the gate electrode and the semiconductor layer. The gate insulating layer is formed of an amorphous composite metal oxide insulating film including one or two or more alkaline-earth metal elements and one or two or more elements selected from a group consisting of Ga, Sc, Y, and lanthanoid except Ce.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.13/515,463, filed Jun. 12, 2012, which is a national phase applicationof PCT/JP2010/073846, filed Dec. 22, 2010, which claims priority toJapanese Patent No. 2009-295425, filed Dec. 25, 2009; Japanese PatentNo. 2010-062244, filed Mar. 18, 2010; Japanese Patent No. 2010-270240,filed Dec. 3, 2010; and Japanese Patent No. 2010-271980, filed Dec. 6,2010, the entire content and disclosure of each of which is incorporatedby reference into the present application.

TECHNICAL FIELD

The present invention relates to field-effect transistors, semiconductormemories, display elements, image display devices, and systems, and moreparticularly to a field-effect transistor having an insulating film madeof a dielectric oxide, and a semiconductor memory, a display element, animage display device, and a system including the field-effecttransistor.

BACKGROUND ART

A field-effect transistor (FET) is a kind of semiconductor devices thatcontrols the electric current between a source electrode and a drainelectrode by applying a voltage to a gate electrode to provide a gatefor the flow of electrons or holes depending on an electric field of achannel.

FETs are used as switching elements and amplifying elements due to theirproperties. Since an FET shows a small gate current and has a flatprofile, it can be easily manufactured or integrated compared to abipolar transistor. Therefore, an FET is now an indispensable element inan integrated circuit used in electronic devices.

There are electronic devices including FETs, of which basic structure isMIS (Metal Insulator Semiconductor) structure. Examples of the devicesare a switching element, a memory, a logic circuit; other examples arean LSI (Large Scale Integrated Circuit) and an AM-TFT (Active MatrixThin Film Transistor), which are formed by integrating theaforementioned elements. In the FETs, silicon oxide, oxynitride, andnitride have been used as gate insulating films and capacitor insulatingfilms for a long time. The insulating films of these silicon compoundsare not only excellent as insulating films, but also have high affinitywith the MIS process.

However, in recent years and continuing, there is demand for electronicdevices that are more highly integrated and that consume less power.Therefore, there has been proposed a technology for using, as theinsulating film, a so-called high-k insulating film that hassignificantly a higher relative permittivity than SiO₂.

For example, in a microscopic MOS (Metal Oxide Semiconductor) devicehaving a gate length of less than or equal to 0.1 μm, when the gateinsulating layer of FET is made of SiO₂, the film thickness needs to beless than or equal to 2 nm, based on the scaling law. However, in thiscase, the gate leakage current caused by a tunnel current becomes alarge problem. One approach to reduce the gate leakage current isincreasing the thickness of the gate insulating layer by using thehigh-k insulating film as the gate insulating layer.

A volatile or non-volatile semiconductor memory is an example of asemiconductor device using the field-effect transistor.

In a volatile memory, the drain electrode of the field-effect transistorand the capacitor are serially connected. By using a high-k insulatingfilm, power consumption can be reduced and high integration is possible.Currently, dielectric layers of capacitors are mainly made of laminatedlayers of SiO₂/SiNx/SiO₂. Thus, there is further demand for insulatingfilms having higher relative permittivity.

The writing/erasing voltage can be reduced in a non-volatilesemiconductor memory, including a first gate insulating layer that is aninsulating film provided between a semiconductor layer and a floatinggate electrode, and a second gate insulating layer that is an insulatingfilm provided between a floating gate electrode and a control gateelectrode. Specifically, the writing/erasing voltage can be reduced as aresult of increasing the coupling ratio by using a high-k insulatingfilm as the second gate insulating film of the non-volatilesemiconductor memory. Currently, second gate insulating layers aremainly made of laminated layers of SiO₂/SiNx/SiO₂. Thus, there isfurther demand for insulating films having a higher relativepermittivity.

In an AM-TFT used in displays, if a high-k insulating film is used inthe gate insulating film, high saturation currents can be attained andthe ON/OFF operation can be controlled by a low gate voltage, so thatthe power consumption can be reduced.

Typically, as materials of a high-k insulating film, metal oxide ofmetals such as Hf, Zr, Al, Y, and Ta have been discussed. Specificexamples are HfO₂, ZrO₂, Al₂O₃, Y₂O₃, Ta₂O₅; silicates of these elements(HfSiO, ZrSiO); aluminates of these elements (HfAlO, ZrAlO), andnitrides of these elements (HfON, ZrON, HfSiON, ZrSiON, HfAlON, ZrAlON).

Meanwhile, in regard to ferroelectric memory materials, a perovskitestructure and related substances have been discussed. The perovskitestructure is expressed by ABO₃, which is typically a combination of adivalent metal ion (A site) and a tetravalent metal ion (B site), or acombination of trivalent metal ions corresponding to both the A site andthe B site. Examples are SrTiO₃, BaZrO₃, CaSnO₃, and LaAlO₃.Furthermore, there are many crystals in which the B site is occupied bytwo kinds of ions, such as SrBi_(0.5)Ta_(0.5)O₃ andBaSc_(0.5)Nb_(0.5)O₃.

Furthermore, there is a series of crystals referred to as a layer typeperovskite structure. This is expressed by (AO)_(m)(BO₂)_(n), in whichan m number of AO layers and an n number of BO₂ layers are laminated.For example, there are Sr₂TiO₄, Sr₃Ti₂O₇, and Sr₄Ti₃O₁₀, with respect toa basic structure of SrTiO₃(m=n=1). According to such crystalstructures, the composition ratio of A ions and B ions may be varied.Accordingly, a wide variety of crystal groups may appear, including thecombination of B site ions. In the present application, a “perovskitestructure related crystal” means a crystal having a perovskite structureor a layer type perovskite structure.

Incidentally, when a polycrystalline material is used as a gateinsulating layer, a large leakage current flows at the interfaces of thecrystal grain boundaries. Therefore, the function of the gate insulatingfilm is degraded. Furthermore, when the crystal system has anisotropy,properties of the transistor may become irregular due to dielectricconstant anisotropy.

Patent documents 1 and 2 disclose methods of decreasing leakage currentsin the gate insulating layer, by using an amorphous insulating film madeof a high-dielectric-constant silicate as the gate insulating layer.

Patent document 3 discloses a method of decreasing leakage currents inthe gate insulating layer, by using an amorphous insulating filmprimarily made of A₂B₂O₇ having a pyrochlore structure, as the gateinsulating layer.

Patent documents 4, 5, and 6 disclose methods of decreasing leakagecurrents in the gate insulating layer, by using laminated filmsincluding a high dielectric constant film as the gate insulating layer.Patent document 7 discloses a method of decreasing leakage currents inthe gate insulating layer, by forming a high dielectric constant film ofepitaxial growth on a substrate, and performing a heating process sothat elements in the substrate and metal oxide elements in the gateinsulating film are mixed together.

Furthermore, patent document 8 discloses a TFT device in which laminatedfilms, including an inorganic oxide film having a high dielectricconstant and an organic polymer film, are used as the gate insulatinglayer.

However, the problem with the insulating film disclosed in patentdocuments 1 and 2 is that the relative permittivity cannot besufficiently increased, because the insulating film has plenty of SiO₂content.

With the material disclosed in patent document 3, the gate insulatinglayer includes a crystalline phase. Therefore, an amorphous phase isformed in the region of an extremely narrow process condition.Accordingly, there are problems in the manufacturing process.

The problem with the methods disclosed in patent documents 4 through 8is that the manufacturing process is complex and manufacturing costs arehigh.

Accordingly, there is a need for a field-effect transistor, asemiconductor memory, a display element, an image display device, and asystem, including an insulating film having a high relative permittivityand a small amount of leakage currents formed by a simple method and atlow cost.

Patent Document 1: Japanese Laid-Open Patent Application No. H11-135774

Patent Document 2: Japanese Patent No. 3637325

Patent Document 3: Japanese Laid-Open Patent Application No. 2002-270828

Patent Document 4: Japanese Laid-Open Patent Application No. 2002-134737

Patent Document 5: Japanese Patent No. 3773448

Patent Document 6: Japanese Laid-Open Patent Application No. 2003-258243

Patent Document 7: Japanese Patent No. 3831764

Patent Document 8: Japanese Laid-Open Patent Application No. 2008-16807

Patent Document 9: Japanese Laid-Open Patent Application No. 2001-319927

Patent Document 10: Japanese Laid-Open Patent Application No.2002-367980

Patent Document 11: Japanese Laid-Open Patent Application No.2004-241751

Patent Document 12: Japanese Laid-Open Patent Application No.2007-165724

Patent Document 13: Japanese Laid-Open Patent Application No. 2008-91904

DISCLOSURE OF INVENTION

Aspects of the present invention provide a semiconductor device, animage display device, a system, insulating film forming ink, a method ofmanufacturing insulating film forming ink, and a method of manufacturinga semiconductor device, that solve or reduce one or more problems causedby the limitations and disadvantages of the related art.

An aspect of the present invention provides a field-effect transistorincluding a substrate; a source electrode, a drain electrode, and a gateelectrode that are formed on the substrate; a semiconductor layer bywhich a channel is formed between the source electrode and the drainelectrode when a predetermined voltage is applied to the gate electrode;and a gate insulating layer provided between the gate electrode and thesemiconductor layer, wherein the gate insulating layer is formed of anamorphous composite metal oxide insulating film including one or two ormore alkaline-earth metal elements and one or two or more elementschosen from a group consisting of Ga, Sc, Y, and lanthanoid except Ce.

With this configuration, an insulating film having a high relativepermittivity and a small amount of leakage currents can be formed by asimple method, and therefore a field-effect transistor, a semiconductormemory, a display element, an image display device, and a system thatare low-voltage-driven, highly integrated, high-resolution, andhigh-luminance, can be provided at low cost.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates a field-effect transistor according to a firstembodiment of the present invention;

FIG. 2 illustrates another example (1) of the field-effect transistoraccording to the first embodiment of the present invention;

FIG. 3 illustrates yet another example (2) of the field-effecttransistor according to the first embodiment of the present invention;

FIG. 4 illustrates yet another example (3) of the field-effecttransistor according to the first embodiment of the present invention;

FIG. 5 illustrates a field-effect transistor according to a secondembodiment of the present invention;

FIG. 6 illustrates a volatile memory according to a third embodiment ofthe present invention;

FIG. 7 illustrates another example (1) of the volatile memory accordingto the third embodiment of the present invention;

FIG. 8 illustrates yet another example (2) of the volatile memoryaccording to the third embodiment of the present invention;

FIG. 9 illustrates yet another example (3) of the volatile memoryaccording to the third embodiment of the present invention;

FIG. 10 illustrates a volatile memory according to a fourth embodimentof the present invention;

FIG. 11 illustrates a non-volatile memory according to a fifthembodiment of the present invention;

FIG. 12 illustrates another example (1) of the non-volatile memoryaccording to the fifth embodiment of the present invention;

FIG. 13 illustrates yet another example (2) of the non-volatile memoryaccording to the fifth embodiment of the present invention;

FIG. 14 illustrates yet another example (3) of the non-volatile memoryaccording to the fifth embodiment of the present invention;

FIG. 15 illustrates a non-volatile memory according to a sixthembodiment of the present invention;

FIG. 16 illustrates an organic electro luminescence display elementaccording to a seventh embodiment of the present invention;

FIG. 17 illustrates another example of the organic electro luminescencedisplay element according to the seventh embodiment of the presentinvention;

FIG. 18 illustrates a liquid crystal element used as a display elementaccording to the seventh embodiment of the present invention;

FIG. 19 illustrates an electrochromic element used as a display elementaccording to the seventh embodiment of the present invention;

FIG. 20 illustrates an electrophoretic element used as a display elementaccording to the seventh embodiment of the present invention;

FIG. 21 illustrates an electrowetting element (1) used as a displayelement according to the seventh embodiment of the present invention;

FIG. 22 illustrates the electrowetting element (2) used as a displayelement according to the seventh embodiment of the present invention;

FIG. 23 is a block diagram of a television device according to an eighthembodiment of the present invention;

FIG. 24 is for describing the television device according to the eighthembodiment of the present invention (1);

FIG. 25 is for describing the television device according to the eighthembodiment of the present invention (2);

FIG. 26 is for describing the television device according to the eighthembodiment of the present invention (3);

FIG. 27 is for describing a display element according to the eighthembodiment of the present invention;

FIG. 28 is for describing an organic EL element according to the eighthembodiment of the present invention;

FIG. 29 is for describing the television device according to the eighthembodiment of the present invention (4);

FIG. 30 is for describing another example (1) of the display elementaccording to the eighth embodiment of the present invention;

FIG. 31 is for describing yet another example (2) of the display elementaccording to the eighth embodiment of the present invention;

FIG. 32 indicates transistor properties of field-effect transistorsaccording to example 1 and comparative example 1;

FIG. 33 illustrates a volatile memory according to example 3;

FIG. 34 illustrates a capacitor formed according to examples 7 and 8 andcomparative example 2;

FIG. 35 indicates properties of the capacitor according to example 7;

FIG. 36 indicates properties of the capacitor according to example 8;

FIG. 37 indicates properties of the capacitor according to comparativeexample 2;

FIG. 38 indicates properties of field-effect transistors according toexample 9 and comparative example 3; and

FIG. 39 is a flowchart of a method of manufacturing the organic ELdisplay element according to example 7.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention are described below with referenceto the accompanying drawings.

The present invention is based on a result of intensive studies made bythe inventors of the present invention. Specifically, the inventors haveformulated an insulating material made of an oxide that is asingle-layer film, has a high dielectric constant, and has a smallamount of leakage currents. Furthermore, the inventors have formed anelectronic device using this insulating material.

That is to say, the present invention is based on a finding that anamorphous phase is stably indicated in a composite metal oxide filmincluding one or two or more alkaline-earth metal elements chosen from agroup consisting of Be, Mg, Ca, Sr, Ba, and Ra; and one or two or moreelements chosen from the other group consisting of Ga, Sc, Y, andlanthanoid except Ce, which is Ga, Sc, Y, La, Pr, Nd, Pm, Sm, Eu, Gd,Tb, Dy, Ho, Er, Tm, Yb, and Lu.

Alkaline-earth metal oxide tends to react to moisture and carbon dioxidein the atmosphere, and easily turns into hydroxide and carbonate.Therefore, alkaline-earth metal oxide alone is inappropriate forapplying to electronic devices. Furthermore, simple metal oxides, suchas Ga₂O₃, Sc₂O₃, Y₂O₃, and Ln₂O₃ are easily crystallized, and thereforethe above-described problem of leakage currents arises. However, theinventors of the present invention have found that an amorphousinsulating film can be formed in the atmosphere in a stable manner andover a wide composition area, with the use of a composite oxideincluding both one or two or more alkaline-earth metal elements chosenfrom a group consisting of Be, Mg, Ca, Sr, Ba, and Ra; and one or two ormore elements chosen from the other group consisting of Ga, Sc, Y, andlanthanoid except Ce. Ce specifically becomes tetravalent in lanthanoid,and forms a crystal having a perovskite structure between Ce and thealkaline-earth metal. Therefore, in order to achieve an amorphous phase,it is preferable that we select the elements among lanthanoid except Ce.

In between the alkaline-earth metal and the Ga oxide, there is a crystalphase such as a spinel structure. Compared to perovskite structurecrystals, these crystals do not precipitate unless the temperature issignificantly high (typically, greater than or equal to 1000° C.).Furthermore, there are no reported stable crystal phases betweenalkaline-earth metal oxides and oxides made of Sc, Y, and lanthanoidexcept Ce. Even after a post process performed under high temperature,crystal rarely precipitates from an amorphous phase. Furthermore, theamorphous phase is even more stabilized when the composite oxide of thealkaline-earth metal elements and the elements chosen from the othergroup consisting of Ga, Sc, Y, and lanthanoid except Ce are formed ofgreater than or equal to three kinds of metal elements.

In consideration of forming a high dielectric constant film, thecomposition ratio of elements such as Ba, Sr, Lu, and La is preferablyincreased.

The composite metal oxide film according to an embodiment of the presentinvention can form an amorphous film over a wide composition range, andtherefore the physical properties can be controlled over a wide range.For example, the relative permittivity is approximately 6 through 20,which is sufficiently higher than SiO₂. The relative permittivity can beadjusted to an appropriate value according to the purpose by selectingthe composition.

Furthermore, the thermal expansion coefficient of the composite metaloxide film is similar to that of both typical wiring materials andsemiconductor materials of 10⁻⁶ through 10⁻⁵. Therefore, even afterrepeating a heating process on the composite metal oxide film accordingto an embodiment of the present invention, the film is less likely topeel off, compared to the case of SiO₂ having a thermal expansioncoefficient of 10⁻⁷. In particular, the composite metal oxide film formsa high quality interface between an oxide semiconductor such as a-IGZO(amorphous indium gallium zinc oxide).

Thus, by using the composite metal oxide film in an insulating film ofan FET, a high-performance semiconductor device can be achieved.

The above-described composite metal oxide film may be formed by vacuumprocesses such as CVD (Chemical Vapor Deposition), ALD (Atomic LayerDeposition), and sputtering. By any of these methods, an amorphous filmmay be formed.

The film can also be formed by preparing ink for forming the abovecomposite metal oxide film, applying or printing the ink on a substrate,and then firing the substrate.

A first type of insulating film forming ink used for forming thecomposite metal oxide film is formed with a solution including one ortwo or more alkaline-earth metal elements and one or two or moreelements chosen from a group consisting of Ga, Sc, Y, and lanthanoid(excluding Ce).

A second type of insulating film forming ink includes one or two or moremetal elements chosen from a group consisting of Al, Ti, Zr, Hf, Ce, Nb,and Ta, adding to the first type of ink.

The insulating film forming ink includes at least one of metal organicacid salt and a metal-organic complex of the above metal. In the presentapplication, the word of “metal-organic complex” includes both anorganometallic compound possessing a metal-carbon bond and a metalcomplex possessing a coordinate bond.

The metal organic acid salt is substituted or non-substitutedcarboxylate salt. Examples are magnesium ethyl-butyrate, calciumpropionate, strontium neodecanoate, barium octylate, lanthanum2-ethylhexanoate, yttrium neodecanoate, cerium 2-ethylhexanoate,zirconium naphthenate, and niobium 2-ethylhexanoate, although not solimited.

The metal-organic complex includes an acetylacetonato derivative, asubstituted or non-substituted phenyl group, or a substituted ornon-substituted alkoxy group. Examples are strontium acetylacetonatohydrate, tris(2,2,6,6-tetramethyl-3,5-heptanedionato)neodymium,tetraethoxy acetylacetonato tantalum, magnesium salicylate, titaniumbutoxide, and aluminum di (s-butoxide) acetoacetic ester chelate,although not so limited.

Furthermore, the metal-organic complex may include a carbonyl group, asubstituted or non-substituted alkyl group, or a substituted ornon-substituted cyclodienyl group. Examples are niobium pentacarbonyl,tris (cyclopentadienyl) yttrium, bis (cyclopentadienyl) dicarbonyl titan(II), tetra benzyl hafnium, and diethyl aluminum, although not solimited.

Furthermore, the insulating film forming ink includes inorganic salt ofthe above metals. Examples are strontium carbonate, scandium nitratehydrate, gallium sulfate, and hafnium (IV) dichloride oxide octahydrate,although not so limited.

As the solvent used in the insulating film forming ink, a solvent inwhich the above metal raw material compound can be stably dissolved ordispersed may be appropriately selected. Examples are toluene, xylene,acetylacetone, isopropanol, ethyl benzoate, N,N-dimethylformamide,propylene carbonate, 2-Ethylhexanoic acid, mineral spirits, dimethylpropylene urea, 4-butyrolactone, 2-methoxyethanol, ethylene glycol, andwater, although not so limited.

The method of applying the insulating film forming ink on the substratemay be conventional methods such as spin coating, inkjet printing, slitcoating, nozzle printing, gravure printing, and micro contact printing.Physical properties of the solution of the insulating film forming inksuch as viscosity are preferably adjusted to values that are appropriatefor the coating process. As examples of a means for adjusting theviscosity, ethylene glycol or dipropylene glycol monomethyl ether may beadded to the solvent as a thickening agent, although not so limited. Byusing an appropriate printing method, the ink can be printed only in aspecified area, so that there is no need to subsequently perform apatterning procedure.

Next, by performing a heating process on the insulating film forming inkapplied on the substrate, the ink can be converted into an oxideinsulating film. The heating process may be performed by a conventionalmethod such as resistance heating, infrared heating, and laser beamradiation. In order to convert the metal raw material compound into anoxide, it is necessary to break the metal-carbon and the oxygen-carbonbond of the metal-oxygen-carbon bond in the metal raw material compound.In order to achieve this, an appropriate method can be used to applyenergy required for the decomposition reaction with heat, light, and soon. There are methods for facilitating the conversion into the oxideinsulating film, such as a method of breaking the chemical bonds in themetal-organic complex by irradiating ultraviolet (UV) light or a methodof facilitating oxidation by turning the atmosphere into an ozoneatmosphere. Furthermore, in order to form a high-density film, thereaction conditions of the metal raw material compound and the boilingpoint of the solvent are preferably appropriately selected, in order toattain fluidity of the reaction intermediate and excessive reactionproducts including carbon, hydrogen, oxygen, and nitrogen.

According to the above procedures, the insulating film according to anembodiment of the present invention can be formed. The insulating filmaccording to an embodiment of the present invention has an amorphousstructure, and the leakage current is considerably low when an electricfield is applied.

First Embodiment

A description is given of a field-effect transistor according to a firstembodiment of the present invention with reference to FIG. 1.

The field-effect transistor according to the first embodiment includesan insulating substrate 11, a gate electrode 12, a gate insulating layer13, a source electrode 14, a drain electrode 15, and a semiconductorlayer 16.

First, the insulating substrate 11 is prepared. The insulating substrate11 may be made of alkali-free glass or silica-glass that is alreadywidely used in flat panel displays. Furthermore, a plastic substratemade of materials such as polycarbonate (PC), polyimide (PI),polyethlene terephthalate (PET), and polyethylene naphthalate(PEN) mayalso be appropriately used as the insulating substrate 11. In order toclean the surface and to improve adhesiveness, a pre-process ispreferably performed by oxygen plasma, UV ozone, UV irradiation andcleaning, etc.

Next, the gate electrode 12 is formed on the insulating substrate 11.Various materials and processes may be used to form the gate electrode12. Examples of materials are metals and alloys such as Mo, Al, and Cu,transparent conducting oxides such as ITO and ATO, and organicconductive materials such as polyethylene dioxythiophene (PEDOT) andpolyaniline (PANI). Examples of processes include forming a film bysputtering, spin coating, or dip coating, and then performing patterningby photolithography, or by performing a printing process such as inkjetprinting, nano-in-printing, and gravure printing, so that a film havinga requested shape is directly formed.

Next, the gate insulating layer 13 is formed. In the present embodiment,the gate insulating layer 13 is a composite metal oxide insulating filmmade of one or two or more alkaline-earth metal elements chosen from agroup consisting of Be, Mg, Ca, Sr, Ba, and Ra; and one or two or moreelements chosen from the other group consisting of Ga, Sc, Y, andlanthanoid except Ce.

The amounts of elements included in the composite metal oxide insulatingfilm are not particularly limited. The composition can be determined soas to satisfy the respective properties required by the field-effecttransistor to be manufactured, such as the dielectric constant,dielectric loss, the thermal expansion coefficient, processcompatibility, and cost. The gate insulating film according to anembodiment of the present invention may have a composition selected froma wide range, and therefore a wide range of requested specifications canbe satisfied.

The process is not particularly limited. For example, a film is formedby a vacuum film forming process such as a CVD method and an ALD method,or a sputtering method, and then a photolithography method is performedto form a requested pattern. The film can be formed by preparing ink forforming the above composite metal oxide film, applying the ink on asubstrate, and then firing the substrate under appropriate conditions.The method of applying the ink may be conventional methods such as spincoating, inkjet printing, slit coating, nozzle printing, gravureprinting, and micro contact printing. By using appropriate printingmethods and conditions, the ink can be printed only in a specified area,so that there is no need to subsequently perform a patterning procedure.An amorphous film can be formed by any of the film forming methods.

Next, the source electrode 14 and the drain electrode 15 are formed.Various materials and processes may be used. Examples of materials aremetals and alloys such as Mo, Al, and Ag, transparent conducting oxidessuch as ITO and ATO, and organic conductive materials such aspolyethylene dioxythiophene (PEDOT) and polyaniline (PANI). Examples ofprocesses include forming a film by sputtering, spin coating, or dipcoating, and then performing patterning by photolithography, or byperforming a printing process such as inkjet printing, nano-in-printing,and gravure printing, so that a film having a requested shape isdirectly formed.

Next, the semiconductor layer 16 is formed so as to form a channelbetween the source electrode 14 and the drain electrode 15. Examples ofthe semiconductor layer 16 are an oxide semiconductor such aspolycrystal silicon (p-Si), amorphous silicon (a-Si), and In—Ga—Zn—O,and an organic semiconductor such as pentacene, although not so limited.Among these, the oxide semiconductor is preferable in consideration ofthe stability of the interface of the gate insulating layer 13 and thesemiconductor layer 16.

The process is not particularly limited. Examples of processes include avacuum film forming process such as sputtering, a pulse laser deposition(PLD) method, a CVD method, and an ALD method, and a solution processsuch as spin coating and dip coating, and then performing patterning byphotolithography, or by performing a printing process such as inkjetprinting, nano-in-printing, and gravure printing, so that a film havinga required shape is directly formed.

According to the above procedures, the field-effect transistor isformed.

In the field-effect transistor according to the present embodiment, thecomposite metal oxide insulating film forming the gate insulating layer13 has an amorphous structure, and has a relative permittivity ofapproximately greater than or equal to six, which is higher than that ofSiO₂. Therefore, the leakage current is decreased, and the field-effecttransistor can be driven at low voltage.

The field-effect transistor shown in FIG. 1 is a so-called bottomgate/bottom contact type. However, the field-effect transistor accordingto the present embodiment of the present invention may be, for example,a bottom gate/top contact type as shown in FIG. 2, a top gate/bottomcontact type as shown in FIG. 3, or a top gate/top contact type as shownin FIG. 4.

Specifically, the bottom gate/top contact type shown in FIG. 2 is formedas follows. A gate electrode 22 made of a metal material is formed on aninsulating substrate 21. A gate insulating layer 23 is formed so as tocover the gate electrode 22. A semiconductor layer 24 is formed on thegate insulating layer 23. A source electrode 25 and a drain electrode 26are formed so that a channel is formed on the gate insulating layer 23.

A top gate/bottom contact type as shown in FIG. 3 is formed as follows.A source electrode 32 and a drain electrode 33 are formed on aninsulating substrate 31. A semiconductor layer 34 is formed so as toform a channel between the source electrode 32 and the drain electrode33. A gate insulating layer 35 is formed so as to cover the sourceelectrode 32, the drain electrode 33, and the semiconductor layer 34. Agate electrode 36 is formed on the gate insulating layer 35.

A top gate/top contact type as shown in FIG. 4 is formed as follows. Asemiconductor layer 42 is formed on an insulating substrate 41. A sourceelectrode 43 and a drain electrode 44 are formed so as to form a channelon the semiconductor layer 42. A gate insulating layer 45 is formed insuch a manner as to cover the source electrode 43, the drain electrode44, and the semiconductor layer 42. A gate electrode 46 is formed on thegate insulating layer 45.

The field-effect transistor according to the present embodiment may beused as a driving circuit in, e.g., a semiconductor memory, a TFT, or adisplay (display element).

Second Embodiment

A description is given of a field-effect transistor according to asecond embodiment of the present invention with reference to FIG. 5.

The field-effect transistor according to the second embodiment includesa semiconductor substrate 51, a gate insulating layer 52, a gateelectrode 53, a gate side wall insulating film 54, a source area 55, adrain area 56, an interlayer insulating film 57, a source electrode 58,and a drain electrode 59.

First, the semiconductor substrate 51 is prepared. The material ofsemiconductor substrate 51 is not particularly limited as long as it isa semiconductor material. For example, Si (silicon) or Ge (germanium) inwhich specified impurities are added may be appropriately used.

Next, the gate electrode 52 is formed on the insulating substrate 51. Inthe present embodiment, the gate insulating layer 52 is a compositemetal oxide insulating film made of one or two or more alkaline-earthmetal elements chosen from a group consisting of Be, Mg, Ca, Sr, Ba, andRa; and one or two or more elements chosen from the other groupconsisting of Ga, Sc, Y, and lanthanoid except Ce.

The amounts of elements included in the composite metal oxide insulatingfilm are not particularly limited. The composition can be determined soas to satisfy the respective properties required by the field-effecttransistor to be manufactured, such as the dielectric constant, thedielectric loss, the thermal expansion coefficient, processcompatibility, and cost. The gate insulating film according to anembodiment of the present invention may have a composition selected froma wide range, and therefore a wide range of requested specifications canbe satisfied.

The process is not particularly limited. For example, a film is formedby a vacuum film forming process such as a CVD method and an ALD method,or a sputtering method, and then a photolithography method is performedto form a requested pattern. The film can be formed by preparing ink forforming the above composite metal oxide film, applying the ink on asubstrate, and then firing the substrate under appropriate conditions.The method of applying the ink may be conventional methods such as spincoating, inkjet printing, slit coating, nozzle printing, gravureprinting, and micro contact printing. By using appropriate printingmethods and conditions, the ink can be printed only in a specified area,so that there is no need to subsequently perform a patterning procedure.An amorphous film can be formed by any of the film forming methods.

Next, the gate electrode 53 is formed. The material and process are notparticularly limited. Examples of materials are polysilicon, metalmaterials such as Al, and a laminated body, which may be formed bylaminating barrier metals such as TiN and TaN laminated on thosematerials. Examples of the process are vacuum film forming processessuch as CVD and sputtering. Furthermore, although not shown, there maybe formed a silicide layer such as NiSi, CoSi, and TiSi on the surfaceof the gate electrode 53 for the purpose of reducing the resistance.

The method of patterning the gate insulating layer 52 and the gateelectrode 53 is not particularly limited. For example, aphotolithography method may be performed, in which a mask is formed withthe use of photoresist, and then dry etching is performed to removeparts of the gate insulating layer 52 and the gate electrode 53 fromareas that are not covered by the mask.

Next, the gate side wall insulating film 54 is formed on the side wallsof the gate insulating layer 52 and the gate electrode 53. The materialand process are not particularly limited. Examples of the materials areinsulating materials such as SiON and SiO₂. Examples of processes arevacuum film forming processes such as CVD and sputtering. The method ofpatterning the gate side wall insulating film 54 is not particularlylimited. In one example, the gate side wall insulating film 54 is formedon the entire substrate, and then the entire surface is etched back bydry etching.

Next, ions are selectively implanted into the semiconductor substrate51, to form the source area 55 and the drain area 56. Although notshown, there may be formed a silicide layer such as NiSi, CoSi, and TiSion the surface of the source area 55 and the drain area 56 for thepurpose of reducing the resistance.

Next, the interlayer insulating film 57 is formed. The material andprocess are not particularly limited. Examples of the materials areinsulating materials such as SiON and SiO₂. Examples of processes vacuumfilm forming processes such as CVD and sputtering. The method ofpatterning the interlayer insulating film 57 is not particularlylimited. In one example, a requested pattern may be formed byphotolithography, so that through holes are formed as shown in FIG. 5.

Next, the source electrode 58 and the drain electrode 59 are formed. Thesource electrode 58 and the drain electrode 59 are formed by filling thethrough holes formed in the interlayer insulating film 57 so as to beconnected with the source area 55 and the drain area 56, respectively.

The material and process are not particularly limited. Examples ofmaterials are metal materials such as Al and Cu. Examples of processesare filling the through holes by a vacuum film forming process such assputtering, and then performing patterning by photolithography, or byfilling the through holes by CVD or a coating method, and thenflattening the parts by CMP (Chemical Mechanical Polishing). A laminatedbody may be formed by laminating barrier metals such as TiN and TaN onthe metal materials. A CVD method may be performed to form W plugs byfilling the through holes with W.

According to the above procedures, the field-effect transistor isformed. In the field-effect transistor according to the presentembodiment, the composite metal oxide insulating film forming the gateinsulating layer 52 has an amorphous structure, and the relativepermittivity is greater than or equal to six, which is higher than thatof SiO₂. Therefore, the leakage current can be decreased, and thefield-effect transistor can be driven at low voltage and can be highlyintegrated.

In the field-effect transistor according to the second embodiment shownin FIG. 5, the semiconductor substrate 51 corresponds to thesemiconductor layer forming a channel between the source area 55 and thedrain area 56.

Furthermore, although not shown, a semiconductor layer made of SiGe maybe formed between the semiconductor substrate 51 made of Si and the gateinsulating layer 52. Furthermore, FIG. 5 illustrates a top gatestructure; however, the gate insulating layer 52 may be used in aso-called double gate structure or a fin type FET.

The field-effect transistor according to the present embodiment may beused in a semiconductor memory, etc.

Third Embodiment

A description is given of a volatile semiconductor memory device (firstexample) according to a third embodiment of the present invention withreference to FIG. 6.

The volatile semiconductor memory device (first example) according tothe present embodiment includes an insulating substrate 61, a gateelectrode 62, a gate insulating layer 63, a source electrode 64, a drainelectrode 65, a semiconductor layer 66, a first capacitor electrode 67,a capacitor dielectric layer 68, and a second capacitor electrode 69.

First, the insulating substrate 61 is prepared. The materials are thesame as those of the substrate 11 of the first embodiment.

Next, the gate electrode 62 is formed on the insulating substrate 61.The materials and processes are the same as those of the gate electrode12 of the first embodiment.

Next, the second capacitor electrode 69 is formed. Various materials andprocesses may be used to form the second capacitor electrode 69.Examples of materials are alloys, metals such as Mo, Al, Cu, and Ru,transparent conducting oxides such as ITO and ATO, and organicconductive materials such as polyethylene dioxythiophene (PEDOT) andpolyaniline (PANI). Examples of processes include forming a film bysputtering, spin coating, or dip coating, and then performing patterningby photolithography, or by performing a printing process such as inkjetprinting, nano-in-printing, and gravure printing, so that a film havinga requested shape is directly formed.

The gate electrode 62 and the second capacitor electrode 69 may beformed simultaneously if they are made with the same materials andprocesses.

Next, the gate insulating layer 63 is formed. In the present embodiment,the gate insulating layer 63 is a composite metal oxide insulating filmmade of one or two or more alkaline-earth metal elements chosen from agroup consisting of Be, Mg, Ca, Sr, Ba, and Ra; and one or two or moreelements chosen from the other group consisting of Ga, Sc, Y, andlanthanoid except Ce.

The amounts of elements included in the composite metal oxide insulatingfilm are not particularly limited. The composition can be determined soas to satisfy the respective properties required by the volatilesemiconductor memory device to be manufactured, such as the dielectricconstant, the dielectric loss, the thermal expansion coefficient,process compatibility, and cost. The gate insulating film according toan embodiment of the present invention may have a composition selectedfrom a wide range, and therefore a wide range of requestedspecifications can be satisfied.

The process is not particularly limited. For example, a film is formedby a vacuum film forming process such as a CVD method, an ALD method,and a sputtering method, and then a photolithography method is performedto form a requested pattern. The film can be formed by preparing ink forforming the above composite metal oxide film, applying the ink on asubstrate, and then firing the substrate under appropriate conditions.The method of applying the ink may be conventional methods such as spincoating, inkjet printing, slit coating, nozzle printing, gravureprinting, and micro contact printing. By using appropriate printingmethods and conditions, the ink can be printed only in a specified area,so that there is no need to subsequently perform a patterning procedure.An amorphous film can be formed by any of the film forming methods.

Next, the capacitor dielectric layer 68 is formed on the secondcapacitor electrode 69. The materials of the capacitor dielectric layer68 are not particularly limited. For example, a high dielectric oxidematerial including Hf, Ta, and La and a ferroelectric material such aslead zirconate titanate (PZT) and strontium bismuth tantalate (SBT) maybe used. The capacitor dielectric layer 68 may be made of the insulatingfilm according to an embodiment of the present invention, i.e., acomposite metal oxide insulating film made of one or two or morealkaline-earth metal elements chosen from a group consisting of Be, Mg,Ca, Sr, Ba, and Ra; and one or two or more elements chosen from theother group consisting of Ga, Sc, Y, and lanthanoid except Ce.

The amounts of elements included in the composite metal oxide insulatingfilm are not particularly limited. The composition can be determined soas to satisfy the respective properties required by the volatilesemiconductor memory device to be manufactured, such as the dielectricconstant, the dielectric loss, the thermal expansion coefficient,process compatibility, and cost. The gate insulating film according toan embodiment of the present invention may have a composition selectedfrom a wide range, and therefore a wide range of requestedspecifications can be satisfied.

The process is not particularly limited. For example, a film is formedby a vacuum film forming process such as a CVD method, an ALD method,and a sputtering method, and then a photolithography method is performedto form a requested pattern. The film can be formed by preparing ink forforming the above composite metal oxide film, applying the ink on asubstrate, and then firing the substrate under appropriate conditions.The method of applying the ink may be conventional methods such as spincoating, inkjet printing, slit coating, nozzle printing, gravureprinting, and micro contact printing. By using appropriate printingmethods and conditions, the ink can be printed only in a specified area,so that there is no need to subsequently perform a patterning procedure.An amorphous film can be formed by any of the film forming methods.

The gate insulating layer 63 and the capacitor dielectric layer 68 maybe formed simultaneously if they are made with the same materials andprocesses.

Next, the source electrode 64 and the drain electrode 65 are formed. Thematerials and the processes are the same as those used for the sourceelectrode 14 and the drain electrode 15 of the first embodiment.

Next, the first capacitor electrode 67 is formed. Various materials andprocesses may be used to form the first capacitor electrode 67. Examplesof materials are alloys, metals such as Mo, Al, Cu, and Ru, transparentconducting oxides such as ITO and ATO, and organic conductive materialssuch as polyethylene dioxythiophene (PEDOT) and polyaniline (PANI).Examples of processes include forming a film by sputtering, spincoating, or dip coating, and then performing patterning byphotolithography, or by performing a printing process such as inkjetprinting, nano-in-printing, and gravure printing, so that a film havinga requested shape is directly formed.

The source electrode 64, the drain electrode 65, and the first capacitorelectrode 67 may be formed simultaneously if they are made with the samematerials and processes.

Next, the semiconductor layer 66 is formed. Examples of thesemiconductor layer 66 are polycrystalline silicon (p-Si), amorphoussilicon (a-Si), an oxide semiconductor such as a-IGZO, and an organicsemiconductor such as pentacene, although not so limited. Among these,the oxide semiconductor is preferable in consideration of the stabilityof the interface of the gate insulating layer 63 and the semiconductorlayer 66. The process is not particularly limited. Examples of processesinclude forming a film by a vacuum film forming process such assputtering, a pulse laser deposition (PLD) method, a CVD method, and anALD method, and a solution process such as spin coating and dip coating,and then performing patterning by photolithography, or by performing aprinting process such as inkjet printing, nano-in-printing, and gravureprinting, so that a film having a requested shape is directly formed.

According to the above procedures, the volatile memory is formed.

From a first point of view, in the volatile memory according to thepresent embodiment, the composite metal oxide insulating film formingthe gate insulating layer 63 has an amorphous structure, and therelative permittivity is greater than or equal to six, which is higherthan that of SiO₂. Therefore, the leakage current can be decreased, andthe volatile memory can be driven at low voltage.

From a second point of view, in the volatile memory according to thepresent embodiment, the composite metal oxide insulating films formingthe gate insulating layer 63 and the capacitor dielectric layer 68 haveamorphous structures, and the relative permittivity is greater than orequal to six, which is higher than that of SiO₂. Therefore, the leakagecurrent can be mitigated, and the volatile memory can be driven at lowvoltage.

In the volatile memory (first example) shown in FIG. 6, the positionalrelationships of the gate electrode 62, the gate insulating layer 63,the source electrode 64, the drain electrode 65, and the semiconductorlayer 66 correspond to a so-called bottom gate/bottom contact type.However, the volatile memory the present embodiment may be, for example,a bottom gate/top contact type as shown in FIG. 7, a top gate/bottomcontact type as shown in FIG. 8, or a top gate/top contact type as shownin FIG. 9.

Furthermore, in the volatile memory (first example) shown in FIG. 6, thefirst capacitor electrode 67, the capacitor dielectric layer 68, and thesecond capacitor electrode 69 have planar structures; however, theseelements may have three dimensional structures to increase the volume ofthe capacitors.

Fourth Embodiment

A description is given of a volatile semiconductor memory device (secondexample) according to a fourth embodiment of the present invention withreference to FIG. 10.

The volatile semiconductor memory device (second example) according tothe present embodiment includes a semiconductor substrate 71, a gateinsulating layer 72, a gate electrode 73, a gate side wall insulatingfilm 74, a source area 75, a drain area 76, a first interlayerinsulating film 77, a bit line electrode 78, a second interlayerinsulating film 79, a first capacitor electrode 80, a capacitordielectric layer 81, and a second capacitor electrode 82.

The semiconductor substrate 71, the gate insulating layer 72, the gateelectrode 73, the gate side wall insulating film 74, the source area 75,the drain area 76, and the first interlayer insulating film 77 can bemade with the same materials and processes as those of the semiconductorsubstrate 51, the gate insulating layer 52, the gate electrode 53, thegate side wall insulating film 54, the source area 55, the drain area56, and the interlayer insulating film 57 of the second embodiment.

In the present embodiment, the gate insulating layer 72 is a compositemetal oxide insulating film made of one or two or more alkaline-earthmetal elements chosen from a group consisting of Be, Mg, Ca, Sr, Ba, andRa; and one or two or more elements chosen from the other groupconsisting of Ga, Sc, Y, and lanthanoid except Ce.

The amounts of elements included in the composite metal oxide insulatingfilm are not particularly limited. The composition can be determined soas to satisfy the respective properties required by the volatilesemiconductor memory device to be manufactured, such as the dielectricconstant, the dielectric loss, the thermal expansion coefficient,process compatibility, and cost. The gate insulating film according toan embodiment of the present invention may have a composition selectedfrom a wide range, and therefore a wide range of requestedspecifications can be satisfied.

The process is not particularly limited. For example, a film is formedby a vacuum film forming process such as a CVD method, an ALD method,and a sputtering method, and then a photolithography method is performedto form a requested pattern. The film can be formed by preparing ink forforming the above composite metal oxide film, applying the ink on asubstrate, and then firing the substrate under appropriate conditions.The method of applying the ink may be conventional methods such as spincoating, inkjet printing, slit coating, nozzle printing, gravureprinting, and micro contact printing. By using appropriate printingmethods and conditions, the ink can be printed only in a specified area,so that there is no need to subsequently perform a patterning procedure.An amorphous film can be formed by any of the film forming methods.

As described above, on the semiconductor substrate 71, the gateinsulating layer 72, the gate electrode 73, the gate side wallinsulating film 74, the source area 75, the drain area 76, and the firstinterlayer insulating film 77 are formed, and then the bit lineelectrode 78 is formed. The material and process are not particularlylimited. Examples of materials are Al and Cu. Examples of processes arefilling the through hole by a vacuum film forming process such assputtering and CVD, and then performing patterning by photolithography,or by filling the through hole by CVD or a coating method, and thenflattening the elements by CMP (Chemical Mechanical Polishing). Alaminated body may be formed by laminating barrier metals such as TiNand TaN on the metal materials. A CVD method may be performed to form Wplugs by filling the through hole with W.

Next, the second interlayer insulating film 79 is formed. The materialsand processes are the same as those of the interlayer insulating film 57of the second embodiment.

Next, the first capacitor electrode 80 is formed. The material andprocess are not particularly limited. Examples of materials are metalmaterials such as Al, Cu, and Ru, and polysilicon. Examples of processesare filling the through hole by a vacuum film forming process such assputtering and CVD, and then performing patterning by photolithography,or by filling the through hole by CVD or a coating method, and thenflattening the elements by CMP (Chemical Mechanical Polishing). Alaminated body may be formed by laminating barrier metals such as TiNand TaN on the metal materials. A CVD method may be performed to form Wplugs by filling the through holes with W.

Next, the capacitor dielectric layer 81 is formed. The materials of thecapacitor dielectric layer 81 are not particularly limited. For example,a high dielectric oxide material including Hf, Ta, and La and aferroelectric material such as lead zirconate titanate (PZT) andstrontium bismuth tantalate (SBT) may be used. The capacitor dielectriclayer 81 may be made of the insulating film according to an embodimentof the present invention, i.e., a composite metal oxide insulating filmmade of one or two or more alkaline-earth metal elements chosen from agroup consisting of Be, Mg, Ca, Sr, Ba, and Ra; and one or two or moreelements chosen from the other group consisting of Ga, Sc, Y, andlanthanoid except Ce.

The amounts of elements included in the composite metal oxide insulatingfilm are not particularly limited. The composition can be determined soas to satisfy the respective properties required by the volatilesemiconductor memory device to be manufactured, such as the dielectricconstant, the dielectric loss, the thermal expansion coefficient,process compatibility, and cost. The gate insulating film according toan embodiment of the present invention may have a composition selectedfrom a wide range, and therefore a wide range of requestedspecifications can be satisfied. The process is not particularlylimited.

For example, a film is formed by a vacuum film forming process such as aCVD method, an ALD method, and a sputtering method, and then aphotolithography method is performed to form a requested pattern. Thefilm can be formed by preparing ink for forming the above compositemetal oxide film, applying the ink on a substrate, and then firing thesubstrate under appropriate conditions. The method of applying the inkmay be conventional methods such as spin coating, inkjet printing, slitcoating, nozzle printing, gravure printing, and micro contact printing.By using appropriate printing methods and conditions, the ink can beprinted only in a specified area, so that there is no need tosubsequently perform a patterning procedure. An amorphous film can beformed by any of the film forming methods.

Next, the second capacitor electrode 82 is formed. The material andprocess are not particularly limited. Examples of materials are metalmaterials such as Al, Cu, and Ru, and polysilicon. Examples of processesare forming films by a vacuum film forming process such as sputteringand CVD, and then performing patterning by photolithography. A laminatedbody may be formed by laminating barrier metals such as TiN and TaN onthe metal materials.

According to the above procedures, the volatile memory is formed.

From a first point of view, in the volatile memory according to thepresent embodiment, the composite metal oxide insulating film formingthe gate insulating layer 72 has an amorphous structure, and therelative permittivity is greater than or equal to six, which is higherthan that of SiO₂. Therefore, the leakage current can be decreased, andthe volatile memory can be highly integrated and can be driven at lowvoltage.

From a second point of view, in the volatile memory according to thepresent embodiment, the composite metal oxide insulating films formingthe gate insulating layer 72 and the capacitor dielectric layer 81 havean amorphous structure, and the relative permittivity is greater than orequal to six, which is higher than that of SiO₂. Therefore, the leakagecurrent can be decreased, and the volatile memory can be highlyintegrated and can be driven at low voltage.

The present embodiment describes a volatile memory having a stack typestructure in which a capacitor is placed at the top of the field-effecttransistor; however, the volatile memory is not so limited. For example,the volatile memory may have a trench type structure in which thecapacitor is placed at the bottom of the field-effect transistor, byforming a groove (not shown) in the semiconductor substrate.

Furthermore, in the volatile memory (second example) shown in FIG. 10,the first capacitor electrode 80, the capacitor dielectric layer 81, andthe second capacitor electrode 82 have planar structures; however, theseelements may have three dimensional structures to increase the volume ofthe capacitors.

Fifth Embodiment

A description is given of a non-volatile semiconductor memory (firstexample) according to a fifth embodiment of the present invention withreference to FIG. 11.

The non-volatile semiconductor memory (first example) according to thepresent embodiment includes an insulating substrate 91, a gate electrode92, a first gate insulating layer 93, a floating gate electrode 94, asecond gate insulating layer 95, a source electrode 96, a drainelectrode 97, and a semiconductor layer 98.

The first gate insulating layer 93 is a so-called inter-gate-electrodeinsulating layer, the second gate insulating layer 95 is a so-calledtunnel insulating layer, and the gate electrode 92 is a so-calledcontrol gate electrode. Based on the conditions of voltage applicationto the source electrode 96, the drain electrode 97, and the gateelectrode 92, according to a tunnel effect, electrons can be inputto/output from the floating gate electrode 94 via the second gateinsulating film 95 that is a tunnel insulating layer, thus functioningas a memory.

A method of forming the non-volatile semiconductor memory according tothe present embodiment is described below.

First, the insulating substrate 91 is prepared. Materials are the sameas those of the insulating substrate 11 of the first embodiment.

Next, the gate electrode 92 is formed on the insulating substrate 91.The materials and processes are the same as those of the gate electrode12 of the first embodiment.

Next, the first gate insulating layer 93 is formed so as to cover thegate electrode 92. In the present embodiment, the first gate insulatinglayer 93 is a composite metal oxide insulating film made of one or twoor more alkaline-earth metal elements chosen from a group consisting ofBe, Mg, Ca, Sr, Ba, and Ra; and one or two or more elements chosen fromthe other group consisting of Ga, Sc, Y, and lanthanoid except Ce.

The amounts of elements included in the composite metal oxide insulatingfilm are not particularly limited. The composition can be determined soas to satisfy the respective properties required by the non-volatilesemiconductor memory device to be manufactured, such as the dielectricconstant, the dielectric loss, the thermal expansion coefficient,process compatibility, and cost. The gate insulating film according toan embodiment of the present invention may have a composition selectedfrom a wide range, and therefore a wide range of requestedspecifications can be satisfied.

The process is not particularly limited. For example, a film is formedby a vacuum film forming process such as a CVD method, an ALD method,and a sputtering method, and then a photolithography method is performedto form a requested pattern. The film can be formed by preparing ink forforming the above composite metal oxide film, applying the ink on asubstrate, and then firing the substrate under appropriate conditions.The method of applying the ink may be conventional methods such as spincoating, inkjet printing, slit coating, nozzle printing, gravureprinting, and micro contact printing. By using appropriate printingmethods and conditions, the ink can be printed only in a specified area,so that there is no need to subsequently perform a patterning procedure.An amorphous film can be formed by any of the film forming methods.

Next, the floating gate electrode 94 is formed on the first gateinsulating layer 93. Various materials and processes may be used to formthe floating gate electrode 94. Examples of materials are alloys, metalssuch as Mo, Al, Cu, and Ru, transparent conducting oxides such as ITOand ATO, and organic conductive materials such as polyethylenedioxythiophene (PEDOT) and polyaniline (PANI). Examples of processesinclude forming a film by sputtering, spin coating, or dip coating, andthen performing patterning by photolithography, or by performing aprinting process such as inkjet printing, nano-in-printing, and gravureprinting, so that a film having a requested shape is directly formed.

Next, the second gate insulating layer 95 is formed so as to cover thefloating gate electrode 94. The material is not particularly limited; anoptimum material may be appropriately selected. For the purpose ofincreasing the coupling ratio, an insulating material having a lowdielectric constant such as SiO₂ or fluorinated polymer is preferablyused. The process is not particularly limited. For example, a vacuumfilm forming process such as sputtering, CVD, and ALD, and a solutionmethod such as spin coating, dye coating, nozzle coating, and inkjetprinting for applying a liquid including metal alkoxide and a metalcomplex and a liquid including polymer may be appropriately used.Furthermore, a requested pattern may be formed by performingphotolithography or printing.

Next, the source electrode 96 and the drain electrode 97 are formed onthe second gate insulating layer 95. The materials and processes are thesame as those of the source electrode 14 and the drain electrode 15 ofthe first embodiment.

Next, the semiconductor layer 98 is formed. The material is notparticularly limited. Examples of the semiconductor layer 98 are anoxide semiconductor such as polycrystal silicon (p-Si), amorphoussilicon (a-Si), and In—Ga—Zn—O, and an organic semiconductor such aspentacene, although not so limited. Among these, the oxide semiconductoris preferable. The process is not particularly limited. Examples ofprocesses include forming a film by a vacuum film forming process suchas sputtering, a pulse laser deposition (PLD) method, a CVD method, andan ALD method, and a solution process such as spin coating and dipcoating, and then performing patterning by photolithography, or byperforming a printing process such as inkjet printing, nano-in-printing,and gravure printing, so that a film having a requested shape isdirectly formed.

According to the above procedures, the non-volatile memory (firstexample) is formed.

In the non-volatile semiconductor memory according to the presentembodiment, the composite metal oxide insulating film forming the firstgate insulating layer 93 has an amorphous structure, and has a relativepermittivity of approximately greater than or equal to six, which ishigher than that of SiO₂. Therefore, the leakage current is decreased,and the voltage used for writing/erasing operations can be reduced.

In the non-volatile memory (first example) shown in FIG. 11, thepositional relationships of the gate electrode 92, the source electrode96, the drain electrode 97, and the semiconductor layer 98 correspond toa so-called bottom gate/bottom contact type. However, the non-volatilememory of the present embodiment may be, for example, a bottom gate/topcontact type as shown in FIG. 12, a top gate/bottom contact type asshown in FIG. 13, or a top gate/top contact type as shown in FIG. 14.

Furthermore, in FIGS. 11 through 14, the gate electrode 92, the firstgate insulating layer 93, and the floating gate electrode 94 have planarstructures; however, these elements may have three dimensionalstructures to increase the volume of the capacitors.

Sixth Embodiment

A description is given of a non-volatile semiconductor memory (secondexample) according to a sixth embodiment of the present invention withreference to FIG. 15.

The non-volatile semiconductor memory (second example) according to thepresent embodiment includes a semiconductor substrate 101, a first gateinsulating layer 102, a gate electrode 103, a second gate insulatingfilm 104, a floating gate electrode 105, a gate side wall insulatingfilm 106, a source area 107, and a drain area 108.

The first gate insulating layer 102 is a so-called inter-gate-electrodeinsulating layer, the second gate insulating layer 104 is a so-calledtunnel insulating layer, and the gate electrode 103 is a so-calledcontrol gate electrode. Based on the conditions of voltage applicationto the source area 107, the drain area 108, and the gate electrode 103,according to a tunnel effect, electrons can be input to/output from thefloating gate electrode 105 via the second gate insulating film 104 thatis a tunnel insulating layer, thus functioning as a memory.

A method of forming the non-volatile semiconductor memory according tothe present embodiment is described below.

First, the semiconductor substrate 101 is prepared. Materials are thesame as those of the semiconductor substrate 51 of the secondembodiment.

Next, the second gate insulating film 104 is formed. The material is notparticularly limited; one example is an insulating material having a lowdielectric constant such as SiO₂. The process is not particularlylimited; examples are a thermal oxidation method and a vacuum filmforming method such as sputtering, CVD, and ALD.

Next, the floating gate electrode 105 is formed. The materials andprocesses are not particularly limited. Examples of materials arepolysilicon, metal materials such as Al, and a laminated body, which maybe formed by laminating barrier metals such as TiN and TaN laminated onthose materials. Examples of processes are vacuum film forming processessuch as CVD and sputtering.

Next, the first gate insulating layer 102 is formed. In the presentembodiment, the first gate insulating layer 102 is a composite metaloxide insulating film made of one or two or more alkaline-earth metalelements chosen from a group consisting of Be, Mg, Ca, Sr, Ba, and Ra;and one or two or more elements chosen from the other group consistingof Ga, Sc, Y, and lanthanoid except Ce.

The amounts of elements included in the composite metal oxide insulatingfilm are not particularly limited. The composition can be determined soas to satisfy the respective properties required by the non-volatilesemiconductor memory device to be manufactured, such as the dielectricconstant, the dielectric loss, the thermal expansion coefficient,process compatibility, and cost. The gate insulating film according toan embodiment of the present invention may have a composition selectedfrom a wide range, and therefore a wide range of requestedspecifications can be satisfied.

The process is not particularly limited. For example, a film is formedby a vacuum film forming process such as a CVD method, an ALD method,and a sputtering method, and then a photolithography method is performedto form a requested pattern. The film can be formed by preparing ink forforming the above composite metal oxide film, applying the ink on asubstrate, and then firing the substrate under appropriate conditions.The method of applying the ink may be conventional methods such as spincoating, inkjet printing, slit coating, nozzle printing, gravureprinting, and micro contact printing. By using appropriate printingmethods and conditions, the ink can be printed only in a specified area,so that there is no need to subsequently perform a patterning procedure.An amorphous film can be formed by any of the film forming methods.

The method of patterning the first gate insulating layer 102, the gateelectrode 103, the second gate insulating film 104, and the floatinggate electrode 105 is not particularly limited; for example, a requestedpattern can be formed by photolithography.

Next, the gate side wall insulating film 106 is formed. The materialsand processes are the same as those of the gate side wall insulatingfilm 54 of the second embodiment. Next, ions are selectively implantedinto the semiconductor substrate 101, to form the source area 107 andthe drain area 108. Although not shown, there may be formed a silicidelayer such as NiSi, CoSi, and TiSi on the surface of the source area 107and the drain area 108 for the purpose of reducing the resistance.

According to the above procedures, the non-volatile memory (secondexample) is formed. In the non-volatile semiconductor memory accordingto the present embodiment, the composite metal oxide insulating filmforming the first gate insulating layer 102 has an amorphous structure,and has a relative permittivity of approximately greater than or equalto six, which is higher than that of SiO₂. Therefore, the leakagecurrent is decreased, and the voltage used for writing/erasingoperations can be reduced.

Furthermore, in FIG. 15, the first gate insulating layer 102, the gateelectrode 103, and the floating gate electrode 105 have planarstructures; however, these elements may have three dimensionalstructures to increase the volume of the capacitors.

Seventh Embodiment

A description is given of a display element according to a seventhembodiment of the present invention with reference to FIGS. 16 through22. The display element according to the present embodiment is anorganic electro luminescence (organic EL) display element.

A description is given of the organic EL display element according tothe present embodiment, with reference to FIG. 16. The organic ELdisplay element according to the present embodiment includes aninsulating substrate 201, a first gate electrode 202, a second gateelectrode 203, a gate insulating layer 204, a first source electrode205, a first drain electrode 206, a second source electrode 207, asecond drain electrode 208, a first semiconductor layer 209, a secondsemiconductor layer 210, a first protection layer 211, a secondprotection layer 212, a partition wall 213, an organic EL layer 214, anupper electrode 215, a sealing layer 216, an adhesive layer 217, and anopposing insulating substrate 218.

The organic EL display element according to the present embodimentincludes an organic EL element 250 as an optical control element and apixel driving circuit 280 including a first field-effect transistor 260and a second field-effect transistor 270. The first field-effecttransistor 260 includes the first gate electrode 202, the gateinsulating layer 204, the first source electrode 205, the first drainelectrode 206, the first semiconductor layer 209, and the firstprotection layer 211. The second field-effect transistor 270 includesthe second gate electrode 203, the gate insulating layer 204, the secondsource electrode 207, the second drain electrode 208, the secondsemiconductor layer 210, and the second protection layer 212.

The pixel driving circuit 280 has a structure including two transistorsand one capacitor, and the first drain electrode 206 is connected to thesecond gate electrode 203. In FIG. 16, as a matter of convenience, acapacitor is formed between the second source electrode 207 and thesecond gate electrode 203; however, the position of forming thecapacitor is actually not so limited. A capacitor having the requiredcapacitance may be appropriately designed/formed at required positions.The composite metal oxide insulating film according to an embodiment ofthe present invention may be used as the capacitor dielectric film. Fromthe viewpoint of process design, the capacitor dielectric film and thegate insulating films of the two transistors are desirably formed withthe same material at the same time.

Next, a description is given of a method of forming the organic ELdisplay element according to the present embodiment.

The first field-effect transistor 260 and the second field-effecttransistor 270 may be formed by the same materials and processes asthose of the field-effect transistor according to the first embodiment.

In the present embodiment, the gate insulating layer 204 is a compositemetal oxide insulating film made of one or two or more alkaline-earthmetal elements chosen from a group consisting of Be, Mg, Ca, Sr, Ba, andRa; and one or two or more elements chosen from the other groupconsisting of Ga, Sc, Y, and lanthanoid except Ce.

The amounts of elements included in the composite metal oxide insulatingfilm are not particularly limited. The composition can be determined soas to satisfy the respective properties required by the organic ELdisplay element to be manufactured, such as the dielectric constant, thedielectric loss, the thermal expansion coefficient, processcompatibility, and cost. The gate insulating film according to anembodiment of the present invention may have a composition selected froma wide range, and therefore a wide range of requested specifications canbe satisfied.

The process is not particularly limited. For example, a film is formedby a vacuum film forming process such as a CVD method, an ALD method,and a sputtering method, and then a photolithography method is performedto form a requested pattern. The film can be formed by preparing ink forforming the above composite metal oxide film, applying the ink on asubstrate, and then firing the substrate under appropriate conditions.The method of applying the ink may be conventional methods such as spincoating, inkjet printing, slit coating, nozzle printing, gravureprinting, and micro contact printing. By using appropriate printingmethods and conditions, the ink can be printed only in a specified area,so that there is no need to subsequently perform a patterning procedure.An amorphous film can be formed by any of the film forming methods.

Various materials and processes may be used to form the first protectionlayer 211 and the second protection layer 212. Examples of materials areinorganic oxides and nitrides such as SiO₂, SiON, and SiN_(X), andinsulating materials such as fluorinated polymer. Examples of processesinclude forming a film by sputtering, CVD and spin coating, and thenperforming patterning by photolithography, or by performing a printingprocess such as inkjet printing, nano-in-printing, and gravure printing,so that a film having a requested shape is directly formed.

Various materials and processes may be used to form the partition wall213. Examples of materials are inorganic oxides and nitrides such asSiO₂, SiON, and SiN_(x), and insulating materials such as acrylic andpolyimide. Examples of processes include forming a film by sputtering,CVD and spin coating, and then performing patterning byphotolithography, or by performing a printing process such as inkjetprinting, nano-in-printing, and gravure printing, so that a film havinga requested shape is directly formed.

Next, a description is given of the organic EL element 250. The organicEL element 250 according to the present embodiment includes the organicEL layer 214, the upper electrode 215, and the second drain electrode208 (lower electrode).

For example, the second drain electrode 208 is made of ITO. The seconddrain electrode 208 may be made of a transparent conducting oxide suchas In₂O₃, SnO₂, ZnO, or a silver (Ag)-neodymium (Nd) alloy.

The organic EL layer 214 includes an electron transporting layer, alight emitting layer, and a hole transporting layer. The upper electrode215 is connected to the electron transporting layer and the second drainelectrode 208 is connected to the hole transporting layer. When apredetermined voltage is applied between the second drain electrode 208and the upper electrode 215, holes and electrons that are implanted fromthe second drain electrode 208 and the upper electrode 215 arerecombined in the light emitting layer, so that the luminescence centersemit light in the layer.

For example, the upper electrode 215 is made of aluminum (Al). The upperelectrode 215 may be made of a magnesium (Mg)-silver (Ag) alloy, analuminum (Al)-lithium (Li) alloy, and an ITO (Indium Tin Oxide).

The method of forming the organic EL element is not particularlylimited, and may be a conventional method. For example, a film is formedby a vacuum film forming process such as a vacuum vapor-depositionmethod and a sputtering method, and by a solution process such as inkjetprinting and nozzle printing.

After forming the pixel driving circuit 280 and the organic EL element250, the sealing layer 216 is formed. Various materials and processesmay be used to form the sealing layer 216. Examples of materials areinorganic oxides and nitrides such as SiO₂, SiON, and SiN_(x). Examplesof processes include a vacuum film forming method such as CVD andsputtering.

Finally, the opposing insulating substrate 218 is adhered via theadhesive layer 217 made of a material such as epoxy resin and acrylicresin, so that the organic EL display element is completed.

In the organic EL display element according to the present embodiment,when the first and second field-effect transistors are turned ON, theorganic EL layer 214 emits light, so that an image is displayed from theinsulating substrate 201 side as indicated by an arrow A. In this case,the insulating substrate 201, the second drain electrode 208, and thegate insulating layer 204 need to be made of transparent materials (ITO,SiO₂, etc.).

In the present embodiment, a description is given of a “bottom emission”type, where light is emitted from the insulating substrate 201; however,the present embodiment is not so limited. The organic EL display elementmay be a “top emission” type, where light is emitted from the opposinginsulating substrate 218, on the opposite side to that of the arrow A.In this case for example, a high reflectance electrode such as a silver(Ag)-neodymium (Nd) alloy is used as the second drain electrode 208, anda semi-transparent electrode such as magnesium (Mg)-silver (Ag) alloythin film is used as the upper electrode 215.

In the present embodiment, the organic EL element 250 is located next tothe pixel driving circuit 280; however, the present embodiment is not solimited. For example, as shown in FIG. 17, the organic EL element 250may be located above the pixel driving circuit 280.

In an organic EL display element shown in FIG. 17, on an insulatingsubstrate 221, the first field-effect transistor 260 and the secondfield-effect transistor 270 are formed. The first field-effecttransistor 260 includes a first gate electrode 222, a gate insulatinglayer 224, a first source electrode 225, a first drain electrode 226, afirst semiconductor layer 229, and a first protection layer 231. Thesecond field-effect transistor 270 includes a second gate electrode 223,the gate insulating layer 224, a second source electrode 227, a seconddrain electrode 228, a second semiconductor layer 230, and a secondprotection layer 232. An interlayer insulating film 233 is formed so asto cover the first field-effect transistor 260 and the secondfield-effect transistor 270. Partition walls 234 are formed on theinterlayer insulating film 233. Meanwhile, the organic EL element formedon the pixel driving circuit 280 including the first field-effecttransistor 260 and the second field-effect transistor 270, includes alower electrode 235, an organic EL layer 236, and an upper electrode237. The second drain electrode 228 and the lower electrode 235 areconnected by a through hole formed in the interlayer insulating film233. A sealing layer 238, an adhesive layer 239, and an opposinginsulating substrate 240 are the same as the sealing layer 216, theadhesive layer 217, and the opposing insulating substrate 218 shown inFIG. 16.

In the present embodiment, the organic EL layer includes the electrontransporting layer, the light emitting layer, and the hole transportinglayer; however, the present embodiment is not so limited. For example,the electron transporting layer and the light emitting layer may beincorporated into a single layer. In another example, an electroninjection layer may be provided between the electron transporting layerand the upper electrode 215. Furthermore, a hole injection layer may beprovided between the hole transporting layer and the second drainelectrode.

In the organic EL display element according to the present embodiment,the composite metal oxide insulating film forming the gate insulatinglayer 204 has an amorphous structure, and has a relative permittivity ofapproximately greater than or equal to six, which is higher than that ofSiO₂. Therefore, the leakage current is mitigated, and the organic ELdisplay element can be operated with low power consumption.

In the above description, the pixel driving circuit driving the displayelements has a structure including two transistors and one capacitor;however, the present embodiment is not so limited. The pixel drivingcircuit may have an optimum structure, for example four transistors andone capacitor or five transistors and two capacitors, etc. In any ofthese cases, the composite metal oxide insulating film according to anembodiment of the present invention may be used in both the gateinsulating films of the transistor and the dielectric film of thecapacitor.

The above describes an organic electro luminescence display device inwhich an organic EL element is used as the optical control element.However, the image display device may be a liquid crystal display deviceby using a liquid crystal element as the optical control element. Anexample of a liquid crystal element shown in FIG. 18 includes apolarization plate 302, a glass substrate 303, a transparent electrode304, an alignment film 305, an alignment film 307, a transparentelectrode 308, a color filter 309, a glass substrate 310, and apolarization plate 311. Furthermore, a liquid crystal layer 306 filledwith a liquid crystal material is provided in the liquid crystalelement. Furthermore, the liquid crystal element is provided with a backlight system 301. A power source 312 applies a voltage between thetransparent electrode. 304 and the transparent electrode 308 to controlthe alignment of the liquid crystal material, and to control thetransmittance of light entering from the back light system 301. Theliquid crystal element is driven by a voltage, and therefore the pixeldriving circuit includes one transistor and one capacitor. In this casealso, the composite metal oxide insulating film according to anembodiment of the present invention may be used in both the gateinsulating films of the transistor and the dielectric film of thecapacitor.

In the present embodiment, the display device may be a reflectivedisplay device, by using, as the optical control element (displayelement), an electrochromic element, an electrophoretic element, and anelectrowetting element.

An example of an electrochromic element shown in FIG. 19 includes aglass substrate 321, a bottom electrode 322, a white reflective layer323, an electrolyte solution or a solid electrolyte 324, anelectrochromic layer 325, a top transparent electrode 326, and a glasssubstrate 327. When a power source 328 applies a predetermined voltagebetween the bottom electrode 322 and the top transparent electrode 326,the electrochromic material is reversibly oxidized or reduced, so thatcolor is produced or erased. Accordingly, the electrochromic elementfunctions as a display element.

Furthermore, an example of an electrophoretic element shown in FIG. 20includes a glass substrate 331, a bottom electrode 332, a display layer333, a top transparent electrode 334, and a glass substrate 335. In thedisplay layer 333, white particles and black particles that have beencharged are dispersed in a solvent. When a power source 336 applies apredetermined voltage between the bottom electrode 332 and the toptransparent electrode 334, the charged particles move according to theelectric field. Accordingly, the electrophoretic element functions as adisplay element.

Furthermore, an example of an electrowetting element shown in FIG. 21includes a white substrate 341, a bottom transparent electrode 342, ahydrophobic insulating layer 343, an oil layer 344, an aqueous solutionlayer 345, a top transparent electrode 346, and a glass substrate 347.The oil layer 344 is colored, and the aqueous solution layer 345 istransparent. When the electrowetting element is turned off the color ofthe oil layer 344 is shown because the aqueous solution layer 345 is atranslucent layer. Then, as shown in FIG. 22, when a power source 348applies a predetermined voltage between the bottom transparent electrode342 and the top transparent electrode 346, electric charges aregenerated on the surface of the hydrophobic insulating layer 343, sothat the surface of the hydrophobic insulating layer 343 becomes ahydrophilic surface. That is to say, the affinity of the hydrophobicinsulating layer 343 with respect to the oil layer 344 decreases, andthe affinity of the hydrophobic insulating layer 343 with respect to theaqueous solution layer 345 increases. Consequently, the overall energyis reduced, so that the oil layer 344 moves in a direction such that thecontact area between the oil layer 344 and the hydrophobic insulatinglayer 343 is minimized. Therefore, the color of the white substrate 341is displayed. According to this principle, the electrowetting elementfunctions as a display element.

The above-described electrochromic element, electrophoretic element, andelectrowetting element may be combined with a color filter, to functionas a reflective color display.

The above electrochromic element is a current-driven element, andtherefore the pixel driving circuit needs to have two or moretransistors and one or more capacitors, similar to the organic ELelement. The electrophoretic element and electrowetting element arevoltage-driven elements, and can therefore include only one transistorand one capacitor. In these cases also, the composite metal oxideinsulating film according to an embodiment of the present invention maybe used in both the gate insulating films of the transistor and thedielectric film of the capacitor.

Eighth Embodiment

Next, with reference to FIGS. 23 through 31, a description is given ofan image display device and a system according to an eighth embodimentof the present invention. FIG. 23 is a schematic diagram of a televisiondevice 500 that is a system according to the eighth embodiment. Theconnection lines in FIG. 23 indicate the flow of primary signals andinformation, and do not express all of the connection relationshipsbetween the blocks.

The television device 500 according to the eighth embodiment includes amain control device 501, a tuner 503, an AD converter (ADC) 504, ademodulating circuit 505, a TS (Transport Stream) decoder 506, an audiodecoder 511, a DA converter (DAC) 512, an audio output circuit 513, aspeaker 514, a video decoder 521, a video OSD synthetic circuit 522, avideo output circuit 523, an image display device 524, an OSD renderingcircuit 525, a memory 531, an operation device 532, a drive interface(drive IF) 541, a hard disk device 542, an optical disk device 543, anIR optical receiver 551, and a communications control device 552.

The main control device 501 controls the entire television device 500,and includes a CPU, a flash ROM, and a RAM. The flash ROM includesprograms described by codes that can be decoded by the CPU, and variouskinds of data used for processes performed by the CPU. Furthermore, theRAM is a work memory.

The tuner 503 selects to broadcast a channel that is set in advance,from among broadcast waves received with an antenna 610.

The ADC 504 converts output signals (analog information) from the tuner503 into digital information.

The demodulating circuit 505 demodulates digital information from theADC 504.

The TS decoder 506 performs TS-decoding on output signals from thedemodulating circuit 505, and separates audio information from videoinformation.

The audio decoder 511 decodes audio information from the TS decoder 506.

The DA converter (DAC) 512 converts output signals from the audiodecoder 511 into analog signals.

The audio output circuit 513 outputs, to the speaker 514, output signalsfrom the DA converter (DAC) 512.

The video decoder 521 decodes video information from the TS decoder 506.

The video OSD synthetic circuit 522 combines output signals from thevideo decoder 521 with output signals from the OSD rendering circuit525.

The video output circuit 523 outputs, to the image display device 524,output signals from the video OSD synthetic circuit 522.

The OSD rendering circuit 525 includes a character generator fordisplaying characters and figures on a display screen of the imagedisplay device 524, and generates signals including display informationin accordance with instructions from the operation device 532 and the IRoptical receiver 551.

The memory 531 is used for temporarily storing AV (Audio-Visual) data.

The operation device 532 includes an input medium (not shown) such as acontrol panel, and receives various information items input by a userand reports the various information items to the main control device501.

The drive IF 541 is a bidirectional communications interface, andconforms to, for example, ATAPI (AT Attachment Packet Interface).

The hard disk device 542 includes a hard disk and a driving device fordriving this hard disk. The driving device records data in the hard diskand reproduces data recorded in the hard disk.

The optical disk device 543 records data in an optical disk (forexample, a DVD), and reproduces data recorded in an optical disk.

The IR optical receiver 551 receives optical signals from a remotecontrol transmitter 620, and reports the optical signals to the maincontrol device 501.

The communications control device 552 controls communications with theInternet. The communications control device 552 can acquire variousinformation items via the Internet.

The image display device 524 includes an indicator 700 and a displaycontrol device 780, as shown in FIG. 24.

As shown in FIG. 25, the indicator 700 includes a display 710 in whichplural (n×m) display elements 702 are arranged in a matrix.

As shown in FIG. 26, the display 710 includes an n number of scanninglines (X0, X1, X2, X3, . . . , Xn-2, Xn-1) arranged equidistantly alongan X axis direction, an m number of data lines (Y0, Y1, Y2, Y3, . . . ,Ym-1) arranged equidistantly along a Y axis direction, and an m numberof current supplying lines (Y0 i, Y1 i, Y2 i, Y3 i, . . . , Ym-1 i)arranged equidistantly along the Y axis direction. The display elements702 can be identified by using the scanning lines and data lines.

As shown in FIG. 27, each of the display elements 702 includes anorganic EL (electro luminescence) element 750, and a pixel drive circuit720 for causing the organic EL element 750 to emit light. That is tosay, the display 710 is a so-called active matrix type organic ELdisplay. Furthermore, the display 710 is a color 32 inch display.However, the size of the display 710 is not so limited.

As shown in FIG. 28, the organic EL element 750 includes an organic ELthin film layer 740, a cathode 712, and an anode 714.

The cathode 712 is made of aluminum (Al). The cathode 712 may also bemade of a magnesium (Mg)-silver (Ag) alloy, an aluminum (Al)-lithium(Li) alloy, and ITO (Indium Tin Oxide).

The anode 714 is made of ITO. The anode 714 may also be made of atransparent conducting oxide such as In₂O₃, SnO₂, and ZnO, and a silver(Ag)-neodymium (Nd) alloy.

The organic EL layer 740 includes an electron transporting layer 742, alight emitting layer 744, and a hole transporting layer 746. The cathode712 is connected to the electron transporting layer 742 and the anode714 is connected to the hole transporting layer 746. When apredetermined voltage is applied between the anode 714 and the cathode712, the light emitting layer 744 emits light.

Furthermore, as shown in FIG. 27, the pixel drive circuit 720 includestwo field-effect transistors 810 and 820, and a capacitor 830.

The field-effect transistor 810 operates as a switch element. A gateelectrode G is connected to a predetermined scanning line, and a sourceelectrode S is connected to a predetermined data line. Furthermore, adrain electrode D is connected to one of the terminals of the capacitor830.

The capacitor 830 is for recording data relevant to the state of thefield-effect transistor 810. The other terminal of the capacitor 830 isconnected to a predetermined current supplying line.

The field-effect transistor 820 is for supplying large currents to theorganic EL element 750. The gate electrode G of the field-effecttransistor 820 is connected to the drain electrode D of the field-effecttransistor 810. A drain electrode D of the field-effect transistor 820is connected to the anode 714 of the organic EL element 750. A sourceelectrode S of the field-effect transistor 820 is connected to apredetermined current supplying line.

When the field-effect transistor 810 is turned on, the organic ELelement 750 is driven by the field-effect transistor 820.

As shown in FIG. 29, the display control device 780 includes an imagedata processing circuit 782, a scanning line driving circuit 784, and adata line driving circuit 786.

The image data processing circuit 782 determines the luminance of pluraldisplay elements 702 in the display 710, based on output signals fromthe video output circuit 523.

The scanning line driving circuit 784 separately applies a voltage toeach of the n scanning lines in response to an instruction from theimage data processing circuit 782.

The data line driving circuit 786 separately applies a voltage to eachof the m data lines in response to an instruction from the image dataprocessing circuit 782.

As apparent from the above description, the television device 500according to the present embodiment has an image data creating deviceincluding the video decoder 521, the video OSD synthetic circuit 522,the video output circuit 523, and the OSD rendering circuit 525.

In the above description, the optical control element is an organic ELelement; however, the present invention is not so limited. The opticalcontrol element may be a liquid crystal element, an electrochromicelement, an electrophoretic element, and an electrowetting element.

For example, when the optical control element is a liquid crystalelement, a liquid crystal display of an active matrix method is used asthe display 710. In this case, the liquid crystal element is avoltage-driven element, and therefore there is no need to have currentsupplying lines as shown in FIG. 30.

An example of such a display element is shown in FIG. 31. Specifically,a pixel drive circuit 730 may include only one field-effect transistor840 and only one capacitor 760. In the field-effect transistor 840, agate electrode G is connected to a predetermined scanning line and asource electrode S is connected to a predetermined data line.Furthermore, a drain electrode D is connected to a pixel electrode of aliquid crystal element 770 and the capacitor 760. In FIGS. 31, 762 and772 denote opposite electrodes (common electrodes) of the capacitor 760and the liquid crystal element 770, respectively.

The field-effect transistor according to the first embodiment is used asthe field-effect transistors 810, 820, and 840 in the presentembodiment. Therefore, a low-power consuming and high-performancetelevision device is attained.

The dielectric films of the capacitors 760 and 830 according to thepresent embodiment are preferably formed by the same process and at thesame time as the gate insulating film of the field-effect transistoraccording to an embodiment of the present invention. In this case, therelative permittivity of the capacitor insulating film is high, andtherefore even if the area is small, it is possible to attain the samecapacitance as the case where a conventional insulating film is used.Accordingly, it is possible to provide a display in which the pixel areais reduced and the display resolution is increased, or a display inwhich the aperture ratio of the pixel is increased and the luminance isincreased.

Furthermore, the field-effect transistor according to the firstembodiment and the volatile memory according to the third embodiment canbe used in the image data processing circuit 782, the scanning linedriving circuit 784, and the data line driving circuit 786 included inthe display control device 780. Accordingly, it is possible to form theindicator 700 including the display 710 in which the display elements702 are arranged in a matrix, and the display control device 780 on thesame plane, and therefore a low-cost television device can be provided.

In the above-described embodiment, the system is a television device;however, the present embodiment is not so limited, as long as the imagedisplay device 524 is included as the device for displaying images andinformation. For example, the system may be a computer system in which acomputer (may be a personal computer) and the image display device 524are connected to each other.

Furthermore, the image display device 524 may be used as display meansin portable information devices such as a mobile phone, a mobile musicplayer, a mobile video player, an electronic book, and a PDA (PersonalDigital Assistant), or in imaging devices such as a still camera and avideo camera. Furthermore, the image display device 524 may be used asdisplay means for various information items in mobile systems ofvehicles, airplanes, trains, and ships. Furthermore, the image displaydevice 524 may be used as display means for various information items inmeasurement devices, analyzing devices, medical equipment, andadvertisement media.

The field-effect transistors, the volatile memories, and thenon-volatile memories according to the first through sixth embodimentsmay also be applied to devices (e.g., an IC card and an ID tag) otherthan a display device or an image display device.

EXAMPLES Example 1

As example 1, a description is given of a field-effect transistoraccording to an embodiment of the present invention. With reference toFIG. 2, a description is given of a method of manufacturing thefield-effect transistor formed according to example 1.

First, the gate electrode 22 was formed to deposit a molybdenum (Mo)film via a metal mask on the insulating substrate 21 made of alkali-freeglass by a DC magnetron sputtering method. Thickness of the film was 100nm.

Next, the gate insulating layer 23 was formed. A magnesium lanthanumcomposite oxide insulating film was deposited by CVD method. A rawmaterial was made by dissolving La(thd)₃ and Mg(thd)₂(thd=2,2,6,6-tetramethyl-3,5-heptanedionato) in solvents oftetraethylene glycol dimethyl ether (tetraglyme) and tetrahydrofuran(THF), respectively. The thickness of the insulating film is 200 nm.

Next, a magnesium indium oxide film as the semiconductor layer 24 wasformed via a metal mask on the gate insulator by a DC magnetronsputtering method at room temperature. The target was an MgIn₂O₄sintered body and the sputtering gas was the mixture of argon andoxygen. The thickness of the formed semiconductor layer 24 wasapproximately 100 nm.

Next, an aluminum film as the source electrode 25 and the drainelectrode 26 was formed by vacuum vapor deposition with the use of ametal mask. Accordingly, the source electrode 25 and the drain electrode26 were formed only in predetermined areas. Furthermore, the thicknessesof the source electrode 25 and the drain electrode 26 were approximately100 nm, so that the channel length was approximately 50 μm and thechannel width was approximately 400 μm.

Next, the semiconductor layer was subjected to a heating process in airat 300° C. for one hour.

Accordingly, the field-effect transistor of example 1 was formed.

Comparative Example 1

Next, as a comparative example 1, a description is given of afield-effect transistor having a conventional structure, with referenceto FIG. 2. The difference between the field-effect transistor accordingto example 1 and the field-effect transistor according to comparativeexample 1 is that the method of forming the gate insulating layer 23 isdifferent; as for the other layers, the same manufacturing method andmaterials were used.

The gate electrode 22 was formed on the insulating substrate 21 by thesame method as that of example 1. Next, a SiO₂ film having a thicknessof 200 nm was formed by a RF sputtering method in conventionalcondition, to form the gate insulating layer 23. Next, by the samemethod as that of example 1, the semiconductor layer 24, the sourceelectrode 25, and the drain electrode 26 were formed and subsequentlyannealed, thereby forming the field-effect transistor according tocomparative example 1.

Example 1 and Comparative Example 1

FIG. 32 indicates transistor properties of the field-effect transistoraccording to example 1 and the field-effect transistor according tocomparative example 1. Both the field-effect transistor according toexample 1 and the field-effect transistor according to comparativeexample 1 have an ON/OFF ratio of greater than or equal to seven digits,and therefore good switching properties are achieved. Specifically, theON/OFF ratio is the current ratio of a current flowing in an ON stateand a current flowing in an OFF state. Furthermore, in the field-effecttransistor according to example 1, a current Id starts increasing whenthe gate voltage V_(g) is approximately 0V, similar to the field-effecttransistor according to comparative example 1. Accordingly, thefield-effect transistor according to example 1 indicates good transistorproperties. Furthermore, as described above, the gate insulating layerof the field-effect transistor according to example 1 has a higherrelative permittivity than that of the field-effect transistor accordingto comparative example 1. Therefore, in the field-effect transistoraccording to example 1, the current I_(ds) that flows in the ON state ishigher than that of the field-effect transistor according to comparativeexample 1.

Furthermore, the magnesium lanthanum composite oxide forming the gateinsulating layer 23 in example 1 showed a relative permittivity ofapproximately nine. This is much higher than the relative permittivityof approximately 3.9 of the SiO₂ film in comparative example 1.Furthermore, a low leakage current property was confirmed. Furthermore,in an X ray diffraction experiment, even when the gate insulating layer23 was heated at 400° C. for one hour, a diffraction peak could not beobserved. Accordingly, an amorphous state was confirmed.

Example 2

A description is given of a field-effect transistor (MOS-FET) accordingto example 2, with reference to FIG. 5. The MOS-FET according to example2 was formed as follows. A liquid raw material was made by dissolvingLa(thd)₃ and Sr(thd)₂ (thd=2,2,6,6-tetramethyl-3,5-heptanedionato) intetraethylene glycol dimethyl ether (tetraglyme) and tetrahydrofuran(THF), respectively. This liquid raw material was applied on the p typeSi substrate 51 by a CVD method to form a lanthanum strontium compositeoxide insulating film having a thickness of 5 nm. Furthermore, a CVDmethod was performed to form a polycrystalline silicon film, and aphotolithography procedure is performed to pattern the polycrystallinesilicon film and the lanthanum strontium composite oxide insulatingfilm, thereby forming the gate insulating layer 52 and the gateelectrode 53. Next, a CVD method was performed to deposit SiON. Then,the entire surface was subjected to dry etching, so that the gate sidewall insulating film 54 was formed. Next, the gate electrode 53 and thegate side wall insulating film 54 were used as a self-alignment mask toimplant phosphorus ions into the p type Si substrate 51. According toion diffusion, the source area 55 and the drain area 56 were formed.Next, a CVD method was performed to deposit SiO₂, and a photolithographyprocedure was performed to form the interlayer insulating film 57 havingcontact holes. Finally, a sputtering method was performed to deposit anAl layer, with which the contact holes were filled. Then, patterning wasperformed by a photolithography procedure, so that the source electrode58 and the drain electrode 59 were formed. By performing the aboveprocedures, the field-effect transistor (MOS-FET) was formed.

The field-effect transistor formed in example 2 showed good transistorproperties and low leakage current properties. The lanthanum strontiumcomposite oxide forming the gate insulating layer 52 formed in example 2showed a relative permittivity of approximately 10, and a low leakagecurrent property was confirmed. Furthermore, in an X ray diffractionexperiment, it was found that an amorphous state is attained.

Example 3

As example 3, a description is given of a volatile memory according toan embodiment of the present invention. With reference to FIG. 33, adescription is given of a method of manufacturing the volatile memoryformed according to example 3.

First, a gate electrode 112 and a second capacitor electrode 113 wereformed on a substrate 111 made of alkali-free glass. Specifically, amolybdenum (Mo) film having a thickness of approximately 100 nm wasformed on the glass substrate 111 by a DC sputtering method.Subsequently, a photoresist was applied, and subjected to prebaking,exposing by a stepper with a photomask, and developing, so that a resistpattern having the same pattern as the gate electrode 112 and the secondcapacitor electrode 113 was formed. Furthermore, RIE (Reactive IonEtching) was performed to remove the molybdenum film from areas wherethe resist pattern was not formed. Subsequently, the resist pattern wasalso removed, so that the gate electrode 112 and the second capacitorelectrode 113 were formed.

Next, a gate insulating layer 114 was formed. Specifically, a liquid rawmaterial was made by dissolving La(thd)₃ and Ba(thd)₂(thd=2,2,6,6-tetramethyl-3,5-heptanedionato) in tetraethylene glycoldimethyl ether (tetraglyme) and tetrahydrofuran (THF), respectively.This liquid raw material was applied on the gate electrode 112 and theglass substrate 111 by a CVD method, to form a barium lanthanumcomposite oxide insulating film having a thickness of 200 nm, so thatthe gate insulating layer 114 was formed. Subsequently, a photoresistwas applied, and the photoresist was subjected to prebaking, exposing bya stepper with a photomask, and developing, so that a resist patternhaving the same pattern as the gate insulating layer 114 was formed.Furthermore, RIE (Reactive Ion Etching) was performed to remove thebarium lanthanum composite oxide insulating film from areas where theresist pattern was not formed. Subsequently, the resist pattern was alsoremoved, so that the gate insulating layer 114 was formed.

Next, a capacitor dielectric layer 115 was formed. Specifically, aliquid raw material was made by dissolving La(thd)₃ and Ba(thd)₂(thd=2,2,6,6-tetramethyl-3,5-heptanedionato) in tetraethylene glycoldimethyl ether (tetraglyme) and tetrahydrofuran (THF), respectively.This liquid raw material was applied on the gate electrode 112 and theglass substrate 111 by a CVD method, to form a barium lanthanumcomposite oxide insulating film having a thickness of 50 nm, so that thecapacitor dielectric layer 115 was formed. Subsequently, a photoresistwas applied, and the photoresist was subjected to prebaking, exposing bya stepper with a photomask, so that a resist pattern having the samepattern as the capacitor dielectric layer 115 was formed. Furthermore,RIE (Reactive Ion Etching) was performed to remove the barium lanthanumcomposite oxide insulating film from areas where the resist pattern wasnot formed. Subsequently, the resist pattern was also removed, so thatthe capacitor dielectric layer 115 was formed.

Next, a source electrode 116 and a drain electrode 117 were formed. Inexample 3, the drain electrode 117 also acts as the first capacitorelectrode in the third embodiment, and forms capacitors together withthe capacitor dielectric layer 115 and the second capacitor electrode113.

Specifically, an ITO film that is a transparent conducting film wasformed on the gate insulating layer 114 and the capacitor dielectriclayer 115 by a DC sputtering method, so that the ITO film had athickness of approximately 100 nm. Subsequently, a photoresist wasapplied on the ITO film, and the photoresist was subjected to prebaking,exposing by a stepper with a photomask, and developing, so that a resistpattern having the same pattern as the source electrode 116 and thedrain electrode 117 was formed. Furthermore, RIE (Reactive Ion Etching)was performed to remove the ITO film from areas where the resist patternwas not formed. Subsequently, the resist pattern was also removed, sothat the source electrode 116 and the drain electrode 117 made from theITO film are formed.

Next, a semiconductor layer 118 was formed. Specifically, an magnesiumindium oxide film having a thickness of approximately 100 nm was formedby a DC sputtering method. Subsequently, a photoresist was applied onthe magnesium indium oxide film, and the photoresist was subjected toprebaking, by a stepper with a photomask, and developing, so that aresist pattern having the same pattern as the semiconductor layer 118was formed. Furthermore, RIE (Reactive Ion Etching) was performed toremove the magnesium indium film from areas where the resist pattern wasnot formed. Subsequently, the resist pattern was also removed, so thatthe semiconductor layer 118 was formed. Accordingly, the semiconductorlayer 118 was formed such that a channel was formed between the sourceelectrode 116 and the drain electrode 117.

According to the above procedures, the volatile memory was formed. Thebarium lanthanum composite oxide forming the gate insulating layer 114and the capacitor dielectric layer 115 of the volatile memory formed inexample 3 showed a relative permittivity of approximately 11, and a lowleakage current property was confirmed. Furthermore, in an X raydiffraction experiment, it was found that an amorphous state wasattained.

Example 4

A description is given of a volatile semiconductor memory according toexample 4, with reference to FIG. 10. The volatile semiconductor memoryaccording to example 4 was formed as follows. A raw material was made bydissolving Y(thd)₃ and Sr(thd)₂(thd=2,2,6,6-tetramethyl-3,5-heptanedionato) in tetraethylene glycoldimethyl ether (tetraglyme) and tetrahydrofuran (THF), respectively.This liquid raw material was applied on the p type Si substrate 71 by aCVD method to form a yttrium strontium composite oxide insulating filmhaving a thickness of 5 nm. Furthermore, a CVD method was performed toform a polycrystalline silicon film, and a photolithography procedurewas performed to pattern the polycrystalline silicon film and theyttrium strontium composite oxide insulating film, thereby forming thegate insulating layer 72 and the gate electrode 73. Next, a CVD methodwas performed to deposit SiON. Then, the entire surface was subjected todry etching, so that the gate side wall insulating film 74 is formed.Next, the gate electrode 73 and the gate side wall insulating film 74were used as a self-alignment mask to implant phosphorus ions into the ptype Si substrate 71. According to ion diffusion, the source area 75 andthe drain area 76 were formed. Next, a CVD method was performed todeposit SiO₂, and a photolithography procedure was performed to form theinterlayer insulating film 77 having contact holes. Then, a CVD methodwas performed to deposit the polycrystalline silicon film, with whichthe contact holes were filled. Then, a photolithography procedure wasperformed to form the bit line electrode 78. Next, a CVD method wasperformed to deposit SiO₂, and a photolithography procedure wasperformed to form the interlayer insulating film 79 having a contacthole above the drain area 76. Next, a CVD method was performed to form apolycrystalline silicon film, and a photolithography procedure wasperformed to form the first capacitor electrode (capacitor lowerelectrode) 80. Next, a raw material was made by dissolving Y(thd)₃ andSr(thd)₂ (thd=2,2,6,6-tetramethyl-3,5-heptanedionato) in tetraethyleneglycol dimethyl ether (tetraglyme) and tetrahydrofuran (THF),respectively. This raw material was used to form a yttrium strontiumcomposite oxide insulating film having a thickness of 30 nm by a CVDmethod, so that the capacitor dielectric layer 81 was formed.Subsequently, a polycrystalline silicon film was formed by a CVD method,so that the second capacitor electrode (capacitor upper electrode) 82was formed.

According to the above procedures, the volatile memory was formed. Theyttrium strontium composite oxide insulating film forming the gateinsulating layer 72 and the capacitor dielectric layer 81 of thevolatile memory formed in example 4 showed a relative permittivity ofapproximately seven, and a low leakage current property was confirmed.Furthermore, in an X ray diffraction experiment, it was found that anamorphous state was attained.

Example 5

As example 5, a description is given of a non-volatile memory accordingto an embodiment of the present invention. With reference to FIG. 11, adescription is given of a method of manufacturing the non-volatilememory formed according to example 5.

First, the gate electrode 92 was formed on the substrate 91 made ofalkali-free glass. Specifically, a molybdenum (Mo) film having athickness of approximately 30 nm was formed on the glass substrate 91 bya DC sputtering method. Subsequently, a photoresist was applied, and thephotoresist was subjected to prebaking, by a stepper with a photomask,and developing, so that a resist pattern having the same pattern as thegate electrode 92 was formed. Furthermore, RIE (Reactive Ion Etching)was performed to remove the molybdenum film from areas where the resistpattern was not formed. Subsequently, the resist pattern was alsoremoved, so that the gate electrode 92 was formed.

Next, the gate insulating layer 93 was formed. Specifically, a liquidraw material was made by dissolving La(thd)₃ and Ca(thd)₂(thd=2,2,6,6-tetramethyl-3,5-heptanedionato) in tetraethylene glycoldimethyl ether (tetraglyme) and tetrahydrofuran (THF), respectively.This liquid raw material was applied on the gate electrode 92 and theglass substrate 91 by a CVD method, to form a calcium lanthanumcomposite oxide insulating film having a thickness of 100 nm, so thatthe gate insulating layer 93 was formed.

Next, the floating gate electrode 94 was formed. Specifically, amolybdenum (Mo) film having a thickness of approximately 15 nm wasformed on the first gate insulating layer 93 by a DC sputtering method.Subsequently, a photoresist was applied, and the photoresist wassubjected to prebaking, exposing by a stepper with a photomask, anddeveloping, so that a resist pattern having the same pattern as thefloating gate electrode 94 was formed. Furthermore, RIE (Reactive IonEtching) was performed to remove the molybdenum film from areas wherethe resist pattern was not formed. Subsequently, the resist pattern wasalso removed, so that the floating gate electrode 94 was formed.

Next, the second gate insulating layer 95 was formed. Specifically, aSiO₂ layer having a thickness of approximately 50 nm was formed by a CVDmethod on the first gate insulating layer 93 and the floating gateelectrode 94, so that the second gate insulating layer 95 was formed.

Next, the source electrode 96 and the drain electrode 97 were formed.Specifically, an ITO film that was a transparent conducting film havinga thickness of approximately 100 nm was formed on the second gateinsulating layer 95 by a DC sputtering method. Subsequently, aphotoresist was applied on the ITO film, and the photoresist wassubjected to prebaking, exposing by a stepper with a photomask, anddeveloping, so that a resist pattern having the same pattern as thesource electrode 96 and the drain electrode 97 was formed. Furthermore,RIE (Reactive Ion Etching) was performed to remove the ITO film fromareas where the resist pattern was not formed. Subsequently, the resistpattern was also removed, so that the source electrode 96 and the drainelectrode 97 made of ITO films were formed.

Next, the semiconductor layer 98 was formed. Specifically, an magnesiumindium oxide film having a thickness of approximately 100 nm was formedby a DC sputtering method. Subsequently, a photoresist was applied onthe magnesium indium oxide film, and the photoresist was subjected toprebaking, exposing by a stepper with a photomask, and developing, sothat a resist pattern having the same pattern as the semiconductor layer98 was formed. Furthermore, RIE (Reactive Ion Etching) was performed toremove the magnesium indium oxide film from areas where the resistpattern was not formed. Subsequently, the resist pattern was alsoremoved, so that the semiconductor layer 98 was formed. Accordingly, thesemiconductor layer 98 was formed such that a channel was formed betweenthe source electrode 96 and the drain electrode 97.

According to the above procedures, the non-volatile memory was formed.The calcium lanthanum composite oxide insulating film forming the gateinsulating layer 93 of the non-volatile memory formed in example 5showed a relative permittivity of approximately eight, and a low leakagecurrent property was confirmed. Furthermore, in an X ray diffractionexperiment, it was found that an amorphous state is attained.

Example 6

A description is given of a non-volatile semiconductor memory accordingto example 6, with reference to FIG. 15. The non-volatile semiconductormemory according to example 6 was formed as follows. An SiO₂ having athickness of 5 nm was formed on the p type Si substrate 101 byperforming thermal oxidation on the surface. Then, the second gateinsulating film 104 that is the second gate insulating layer was formedby performing photolithography. Next, a CVD method was performed to forma polycrystalline silicon film, and a photolithography procedure wasperformed to form the floating gate electrode 105.

Next, a raw material was made by dissolving a powder mixture of Y(thd)₃and Sr(thd)₂ (thd=2,2,6,6-tetramethyl-3,5-heptanedionato) in a mixedsolvent of tetrahydrofuran (THF) and ethylene glycol dimethyl ether(DME). This raw material was applied by a CVD method to form a bariumstrontium composite oxide insulating film of 25 nm, and aphotolithography procedure was performed to form the first gateinsulating layer 102. Next, a CVD method was performed to form apolycrystalline silicon film, and a photolithography procedure wasperformed to form the gate electrode 103.

Next, a CVD method was performed to deposit SiON. Then, the entiresurface was subjected to dry etching, so that the gate side wallinsulating film 106 was formed. Next, the gate electrode 103 and thegate side wall insulating film 106 were used as a self-alignment mask toimplant phosphorus ions into the p type Si substrate 101. According toion diffusion, the source area 107 and the drain area 108 were formed.

According to the above procedures, the non-volatile memory was formed.The barium strontium composite oxide insulating film forming the firstgate insulating layer 102 of the non-volatile memory formed in example 6showed a relative permittivity of approximately seven, and a low leakagecurrent property was confirmed. Furthermore, in an X ray diffractionexperiment, it was found that an amorphous state was attained.

Example 7

Next, as example 7, a description is given of a capacitor according toan embodiment of the present invention. This capacitor may be used inthe one-transistor/one-capacitor circuit for driving the liquid crystalelement according to the seventh embodiment, or the volatile memoryaccording to the third embodiment. The following description is givenwith reference to FIG. 34.

First, an aluminum film having a thickness of approximately 100 nm wasformed on a substrate 901 made of alkali-free glass via a metal mask byvacuum vapor deposition, to form a lower capacitor electrode 902 havinga requested shape.

Next, a magnesium lanthanum oxide insulating thin film was formed, whichbecomes a capacitor dielectric layer 903. First, ink for forming anoxide insulating film was manufactured. Specifically, 0.8 ml ofmagnesium 2-ethylhexanoate solution in toluene (Mg content 3 wt %,STREM12-1260) and 2 ml of lanthanum 2-ethylhexanoate solution in toluene(La content 7 wt %, 122-03371 manufactured by Wako Pure ChemicalIndustries, Ltd.) were mixed together. Furthermore, 3 ml of toluene wasadded to dilute this mixture. Accordingly, colorless, transparent inkfor forming a magnesium lanthanum oxide insulating film was prepared.Next, this ink was applied onto the substrate 901 onto which the lowercapacitor electrode 902 had been formed by spin coating (rotating at1000 rpm for five seconds, and then rotating at 3000 rpm for 20seconds). Then, a heating process was performed in air (for one houreach at 200° C., 300° C., and 400° C.). Accordingly, a magnesiumlanthanum oxide insulating thin film having a thickness of 354 nm wasformed.

Next, an aluminum film having a thickness of approximately 100 nm wasformed via a metal mask by vacuum vapor deposition, to form an uppercapacitor electrode 904.

FIG. 35 indicates relationships between the frequency of the appliedelectric field and the relative permittivity ε of the capacitor formedin example 7, and the relationship between the frequency of the appliedelectric field and the dielectric loss tan δ of the capacitor formed inexample 7. As shown in FIG. 35, the relative permittivity ε of thecapacitor formed in example 7 is greater than or equal to 6.1 in theregion ranging from 100 Hz through 1 MHz, and therefore a high relativepermittivity is confirmed. Furthermore, it is also confirmed that thedielectric loss tan δ is low, at less than or equal to approximately 2%,in the region ranging from 100 Hz through 100 kHz.

Example 8

Next, as example 8, a description is given of a capacitor according toan embodiment of the present invention. Similar to example 7, thiscapacitor may be used in the one-transistor/one-capacitor circuit fordriving the liquid crystal element according to the seventh embodiment,or the volatile memory according to the third embodiment. The followingdescription is given with reference to FIG. 34.

First, an aluminum film having a thickness of approximately 100 nm wasformed on a substrate 901 made of alkali-free glass via a metal mask byvacuum vapor deposition, to form a lower capacitor electrode 902 havinga requested shape.

Next, a strontium lanthanum oxide insulating thin film is formed, whichbecomes a capacitor dielectric layer 903. First, ink for forming anoxide insulating film was manufactured. Specifically, 4.4 ml ofstrontium 2-ethylhexanoate solution in toluene (Sr content 2 wt %,195-09561 manufactured by Wako Pure Chemical Industries, Ltd.) and 2 mlof lanthanum 2-ethylhexanoate solution in toluene (La content 7 wt %,122-03371 manufactured by Wako Pure Chemical Industries, Ltd.) weremixed together. Furthermore, 6 ml of toluene was added to dilute thismixture. Accordingly, colorless, transparent ink for forming a strontiumlanthanum oxide insulating film was prepared. Next, this ink was appliedonto the substrate 901 onto which the lower capacitor electrode 902 wasformed by spin coating (rotating at 1000 rpm for five seconds, and thenrotating at 3000 rpm for 20 seconds). Then, a heating process wasperformed in air (for one hour each at 200° C., 300° C., and 400° C.).Accordingly, a strontium lanthanum oxide insulating thin film having athickness of 180 nm was formed.

Next, an aluminum film having a thickness of approximately 100 nm wasformed via a metal mask by vacuum vapor deposition, to form an uppercapacitor electrode 904.

FIG. 36 indicates relationships between the frequency of the appliedelectric field and the relative permittivity ε of the capacitor formedin example 8, and the relationship between the frequency of the appliedelectric field and the dielectric loss tan δ of the capacitor formed inexample 8. As shown in FIG. 36, the relative permittivity ε of thecapacitor formed in example 8 is greater than or equal to 9.7 in theregion ranging from 100 Hz through 1 MHz, and therefore a high relativepermittivity is confirmed. Furthermore, it is also confirmed that thedielectric loss tan δ is low, at less than or equal to approximately 1%in the region ranging from 100 Hz through 100 kHz.

Comparative Example 2

Next, a description is given of a capacitor formed in comparativeexample 2. The structure of the capacitor formed in comparative example2 is the same as those of examples 7 and 8 illustrated in FIG. 34.

In the capacitor of comparative example 2, an aluminum film having athickness of approximately 100 nm was formed on a substrate 901 made ofalkali-free glass via a metal mask by vacuum vapor deposition, to form alower capacitor electrode 902 having a requested shape.

Then, a SiO₂ film having a thickness of approximately 285 nm was formedby RF magnetron sputtering to form an insulating film 903. Then, analuminum film having a thickness of approximately 100 nm was formed viaa metal mask by vacuum vapor deposition, to form an upper capacitorelectrode 904.

FIG. 37 indicates relationships between the frequency of the appliedelectric field and the relative permittivity ε of the capacitor formedin comparative example 2, and the relationship between the frequency ofthe applied electric field and the dielectric loss tan δ of thecapacitor formed in comparative example 2. As shown in FIG. 37, thedielectric loss tan δ of the capacitor formed in comparative example 2is low, at less than or equal to approximately 1% in the region up to250 kHz. However, the relative permittivity ε is approximately 3.9 inthe region ranging from 100 Hz through 1 MHz, which is a lower valuethan those of examples 7 and 8.

Example 9

Next, as example 9, a description is given of a field-effect transistoraccording to an embodiment of the present invention with reference toFIG. 2. The field-effect transistor of example 9 was formed as follows.First, an aluminum film having a thickness of approximately 100 nm wasformed on the substrate 21 made of alkali-free glass via a metal mask byvacuum vapor deposition, to form the gate electrode 22. Next, by thesame method as that of example 8, the gate insulating layer 23 made of astrontium lanthanum oxide and having a thickness of 230 nm was formed.Next, an MgIn₂O₄ film which becomes the semiconductor layer 24 wasformed in room temperature by DC magnetron sputtering. The sputteringgas was a mixture of argon and oxygen, and a film having a thickness of100 nm was formed in a requested region with the use of a metal mask.Next, an aluminum film having a thickness of 100 nm was formed via ametal mask by vacuum vapor deposition, so that the source electrode 25and the drain electrode 26 were formed. The channel length L was 50 μmand the channel width W was 400 μm. Finally, a heating process wasperformed in air at 300° C. for one hour. Accordingly, the field-effecttransistor of example 9 was formed.

Comparative Example 3

Next, as comparative example 3, a description is given of a field-effecttransistor having a conventional structure, with reference to FIG. 2.The difference between the field-effect transistor according to example9 and the field-effect transistor according to comparative example 3 isthe method of forming the gate insulating layer 23; as for the otherlayers, the same manufacturing method and materials were used.

The gate electrode 22 was formed on the insulating substrate 21 by thesame method as that of example 9. Subsequently, a SiO₂ film having athickness of 200 nm was formed by RF magnetron sputtering, to form thegate insulating layer 23. Subsequently, by the same method as that ofexample 9, the semiconductor layer 24, the source electrode 25, and thedrain electrode 26 were formed. Finally, a heating process was performedin air at 300° C. for one hour, similar to example 9. Accordingly, thefield-effect transistor according to comparative example 3 was formed.

Example 9 and Comparative Example 3

FIG. 38 indicates the relationship between a gate voltage V_(g) and aninter-source-drain current I_(ds) in a case where an inter-source-drainvoltage V_(d) is 20 V, in the field-effect transistor according toexample 9 and the field-effect transistor according to comparativeexample 3. As shown in FIG. 38, both the field-effect transistoraccording to example 9 and the field-effect transistor according tocomparative example 3 have an ON/OFF ratio of greater than or equal toeight digits, and therefore TFT properties with good switchingproperties are achieved. Furthermore, in the field-effect transistoraccording to example 9, the ON current is greater than or equal to twotimes as that of the field-effect transistor according to comparativeexample 3. This is because the relative permittivity of the gateinsulating film in example 9 is greater than or equal to two times asthat of the gate insulating film in comparative example 3.

Example 10

Next, a description is given of an image display device according to anembodiment of the present invention, as example 10. The image displaydevice according to example 10 is an organic EL display deviceillustrated in FIG. 16. A method of manufacturing the organic EL displaydevice according to example 10 is described with reference to FIG. 39.

In step S102, the first gate electrode 202 and the second gate electrode203 were formed. Specifically, on the glass substrate 201 made ofalkali-free glass, a molybdenum (Mo) film having a thickness ofapproximately 100 nm was formed by DC sputtering. Subsequently, aphotoresist was applied to form a resist pattern having the same patternas that to be formed. The photoresist was subjected to prebaking,exposing by a stepper with a photomask, and developing. Furthermore, RIE(Reactive Ion Etching) was performed to remove the molybdenum film fromareas where the resist pattern was not formed. Subsequently, the resistpattern was also removed, so that the first gate electrode 202 and thesecond gate electrode 203 were formed.

Next, in step S104, the gate insulating layer 204 was formed.Specifically, a liquid raw material was made by dissolving La(thd)₃ andMg(thd)₂ (thd=2,2,6,6-tetramethyl-3,5-heptanedionato) in tetraethyleneglycol dimethyl ether (tetraglyme) and tetrahydrofuran (THF),respectively. This liquid raw material was applied on the first gateelectrode 202, the second gate electrode 203, and the glass substrate201 by a CVD method, to form a magnesium lanthanum composite oxideinsulating film having a thickness of 200 nm. Subsequently, aphotoresist was applied to form a resist pattern having the same patternas that to be formed. The photoresist was subjected to prebaking,exposing by a stepper with a photomask, and developing. Furthermore, RIE(Reactive Ion Etching) was performed to remove the magnesium lanthanumcomposite oxide insulating film from areas where the resist pattern wasnot formed. Subsequently, the resist pattern was also removed, so thatthe gate insulating film 204 having through holes was formed on thesecond gate electrode 203.

Next, in step S106, the first source electrode 205, the second sourceelectrode 207, the first drain electrode 206, and the second drainelectrode 208 were formed. Specifically, an ITO film which was atransparent conductive film having a thickness of approximately 100 nmwas formed on the gate insulating layer 204 by DC sputtering.Subsequently, a photoresist was applied on the ITO film. The photoresistwas subjected to prebaking, exposing by a stepper with a photomask, anddeveloping, thereby forming a resist pattern having the same pattern asthat to be formed. Furthermore, RIE (Reactive Ion Etching) was performedto remove the ITO film from areas where the resist pattern was notformed. Subsequently, the resist pattern was also removed, so that thefirst source electrode 205, the second source electrode 207, the firstdrain electrode 206, and the second drain electrode 208 made of ITOfilms were formed. Accordingly, the first drain electrode 206 and thesecond gate electrode 203 were connected.

Next, in step S108, the first semiconductor layer 209 and the secondsemiconductor layer 210 were formed. Specifically, a magnesium indiumoxide film having a thickness of approximately 100 nm was formed by DCsputtering. Subsequently, a photoresist was applied on the magnesiumindium film. The photoresist was subjected to prebaking, exposing by astepper with a photomask, and developing, thereby forming a resistpattern having the same pattern as that to be formed. Furthermore, RIE(Reactive Ion Etching) was performed to remove the magnesium indiumoxide film from areas where the resist pattern was not formed.Subsequently, the resist pattern was also removed, so that the firstsemiconductor layer 209 and the second semiconductor layer 210 wereformed. Accordingly, the first semiconductor layer 209 was formed suchthat a channel was formed between the first source electrode 205 and thefirst drain electrode 206, and the second semiconductor layer 210 wasformed such that a channel was formed between the second sourceelectrode 207 and the second drain electrode 208.

Next, in step S110, the first protection layer 211 and the secondprotection layer 212 were formed. Specifically, photosensitive fluorineresin was applied on the entire substrate. The photosensitive fluorineresin is subjected to prebaking, exposing by a stepper with a photomask,and developing, so that a requested pattern was formed. Thephotosensitive fluorine resin was then subjected to postbaking.Accordingly, the first protection layer 211 and the second protectionlayer 212 having a thickness of approximately 400 nm were formed.

Next, in step S112, the partition wall 213 was formed. Specifically, onthe entire substrate, a photosensitive polyimide material was applied.The photosensitive polyimide material was subjected to prebaking,exposing by a stepper with a photomask, and developing, so that arequested pattern was formed. The photosensitive polyimide material wasthen subjected to postbaking. Accordingly, the partition wall 213 havinga thickness of approximately 1 μm was formed.

Next, in step S114, the organic EL layer 214 was formed an area wherethe partition wall 213 was not formed, with the use of an inkjetprinter.

Next, in step S116, the top electrode 215 was formed. Specifically, MgAgwas deposited by vacuum vapor deposition, so that the top electrode 215was formed.

Next, in step S118, the sealing layer 216 was formed. Specifically, anSiO₂ film having a thickness of approximately 2 μm was formed by CVD, sothat the sealing layer 216 was formed.

Next, in step S120, the opposing insulating substrate 218 was adhered.Specifically, the adhesive layer 217 was formed on the sealing layer216, and the opposing insulating substrate 218 made of alkali-free glasswas adhered to the adhesive layer 217. Accordingly, a display panel ofthe organic EL display device according to example 7 was formed as shownin FIG. 16.

Next in step S122, a display control device was connected. Specifically,a display control device (not shown) was connected to the display panelso that images can be displayed on the display panel. Accordingly, animage display system including the organic EL display device was formed.

The organic EL display device formed in example 7 can be driven at lowvoltage, and therefore power consumption of the image display system canbe reduced.

The present invention is not limited to the specific embodimentsdescribed herein, and variations and modifications may be made withoutdeparting from the scope of the present invention.

The present application is based on Japanese Priority Applications No.2009-295425 filed on Dec. 25, 2009, No. 2010-062244 filed on Mar. 18,2010, No. 2010-270240 filed on Dec. 3, 2010, and No. 2010-271980 filedon Dec. 6, 2010 with the Japan Patent Office, the entire contents ofwhich are hereby incorporated by reference.

The invention claimed is:
 1. A field-effect transistor comprising: agate insulating film, wherein the gate insulating film includes acomposite oxide film including: one or more alkaline-earth metalelements selected from a group consisting of Be, Mg, Ca, Sr, Ba, and Ra,and one or more first metal elements selected from a group consisting ofSc, Y, and lanthanoid except Ce, and one or more second metal elementsselected from a group consisting of Al, Zr, Hf, Ce, Nb, and Ta in thecomposite oxide film, wherein a number of atoms in the one or more firstmetal elements is the largest among the one or more alkaline-earth metalelements and the one or more metal elements in the gate insulating film,and a number of atoms in the one or more first metal elements is greaterthan or equal to a number of atoms in the one or more second metalelements in the gate insulating film.
 2. The field-effect transistoraccording to claim 1, further comprising a semiconductor layer, thesemiconductor being an oxide semiconductor.
 3. The field-effecttransistor according to claim 1, further comprising a substrate, thesubstrate being an insulating substrate.
 4. The field-effect transistoraccording to claim 1, further comprising a substrate, the substratebeing a semiconductor substrate.
 5. A volatile semiconductor memorycomprising: the field-effect transistor according to claim 1; a firstcapacitor electrode connected to a drain electrode of the field-effecttransistor; a second capacitor electrode; and a capacitor dielectriclayer provided between the first capacitor electrode and the secondcapacitor electrode.
 6. The volatile semiconductor memory according toclaim 5, wherein the capacitor dielectric layer is formed of anamorphous composite metal oxide insulating film including one or two ormore alkaline-earth metal elements and one or two or more elementsselected from a group consisting of Ga, Sc, Y, and lanthanoid except Ce.7. A non-volatile semiconductor memory comprising: the field-effecttransistor according to claim 1, wherein a second gate insulating layerand a floating gate electrode are provided between a semiconductor layerand the gate insulating layer.
 8. A display element comprising: anoptical control element whose optical output is controlled in accordancewith driving signals; and a driving circuit that drives the opticalcontrol element, the driving circuit including the field-effecttransistor according to claim
 1. 9. The display element according toclaim 8, wherein the optical control element includes an organic electroluminescence element.
 10. The display element according to claim 8,wherein the optical control element includes a liquid crystal element.11. The display element according to claim 8, wherein the opticalcontrol element includes an electrochromic element.
 12. The displayelement according to claim 8, wherein the optical control elementincludes an electrophoretic element.
 13. The display element accordingto claim 8, wherein the optical control element includes anelectrowetting element.
 14. An image display device for displaying animage in accordance with image data, comprising: a plurality of thedisplay elements according to claim 8 arranged in a matrix; a pluralityof wirings that separately apply gate voltages to the field-effecttransistors included in the plural display elements; and a displaycontrol device that separately controls the gate voltages of thefield-effect transistors via the plural wirings, in accordance with theimage data.
 15. A system comprising: the image display device accordingto claim 14; and an image data creating device that creates the imagedata based on image information to be displayed, and that outputs theimage data to the image display device.
 16. The field-effect transistoraccording to claim 1, wherein a thermal coefficient of expansion of thegate insulating film is between 10⁻⁶ and 10⁻⁵.
 17. The field-effecttransistor according to claim 1, wherein the one or more second metalelements are selected from the group consisting of Al, Zr, Hf, and Ce.18. A field-effect transistor comprising: a gate insulating film,wherein the gate insulating film includes a composite oxide filmincluding: one or more alkaline-earth metal elements selected from agroup consisting of Mg, Ca, and Sr, one or more first metal elementsselected from a group consisting of Sc, Y, and lanthanoid except Ce, andone or more second metal elements selected from a group consisting ofAl, Zr, Hf, Ce, Nb, and Ta in the composite oxide film, and wherein anumber of atoms in the one or more first metal elements is greater thanor equal to a number of atoms in the one or more alkaline-earth metalelements in the composite oxide film, and a number of atoms in the oneor more first metal elements is greater than or equal to a number ofatoms in the one or more second metal elements in the composite oxidefilm.
 19. The field-effect transistor according to claim 18, furthercomprising a semiconductor layer, the semiconductor being an oxidesemiconductor.
 20. The field-effect transistor according to claim 18,further comprising a substrate, the substrate being an insulatingsubstrate.
 21. The field-effect transistor according to claim 18,further comprising a substrate, the substrate being a semiconductorsubstrate.
 22. The field-effect transistor according to claim 18,wherein a thermal coefficient of expansion of the composite oxide filmis between 10⁻⁶ and 10⁻⁵.
 23. The field-effect transistor according toclaim 18, wherein the one or more second metal elements are selectedfrom the group consisting of Al, Zr, Hf, and Ce.
 24. A field-effecttransistor comprising: a gate insulating film, wherein the gateinsulating film includes a composite oxide film including: one or morealkaline-earth metal elements selected from a group consisting of Be,Mg, Ca, Sr, and Ra, one or more first metal elements selected from agroup consisting of Ga, Sc, Y, and lanthanoid except Ce, and one or moresecond metal elements selected from a group consisting of Al, Zr, Hf,Ce, Nb, and Ta in the composite oxide film, wherein a number of atoms inthe one or more first metal elements is greater than or equal to anumber of atoms in the one or more alkaline-earth metal elements in thecomposite oxide film, and wherein a number of atoms in the one or morefirst metal elements is greater than or equal to a number of atoms inthe one or more second metal elements in the composite oxide film. 25.The field-effect transistor according to claim 24, further comprising asemiconductor layer, the semiconductor being an oxide semiconductor. 26.The field-effect transistor according to claim 24, further comprising asubstrate, the substrate being an insulating substrate.
 27. Thefield-effect transistor according to claim 24, further comprising asubstrate, the substrate being a semiconductor substrate.
 28. Thefield-effect transistor according to claim 24, wherein a thermalcoefficient of expansion of the composite oxide film is between 10⁻⁶ and10⁻⁵.
 29. The field-effect transistor according to claim 24, wherein theone or more second metal elements are selected from the group consistingof Al, Zr, Hf, and Ce.